RAID 1 Reliablity

Yesterday I setup new Windows Server 2008 R2 Standard with 2x 1TB SATA drives and 2x Intel S3500 SSD. I installed OS on SSD and Software RAID 1 on both SSD/SATA drives. Today I placed some data on the SATA drive (D: drive) and when I tried to access the
data from the drive I got read error. Disk management shows error that 1st SATA drive needs replacement. When I tried to break the mirror I got another error message that The last healthy plex cannot be removed.
So I still have to replace the drive and my question is since RAID 1 mirror data on both the drives and in case of a single drive failure it should retain the data, so in my case why did it show the read error?

Hi VikasRana,
Would you please let us know current situation of this issue? Just check if Milos's suggestion can help you. If any update, please feel free to let us know.
Best regards,
Justin Gu
Please remember to mark the replies as answers if they help and unmark them if they provide no help. If you have feedback for TechNet Support, contact [email protected]

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Raid 0 reliability

I tried a striping raid with two 120 GG hard drives ca. 3 years ago. It failed miserably after a while and I lost the data [had, of course, backups].
How reliable has it become with the OS improvements sincs?
Jurgen

Do some more research, reading, and searching.
Apple RAID card doesn't work with BootCamp.
Don't mix drives in a RAID.
There is no 500GB Raptor.
SATA drives are 7.2K.
Potential boot drives, tests, RAID.
http://www.barefeats.com/harper9.html
http://www.barefeats.com/hard101.html
http://www.barefeats.com/harper13.html
http://www.barefeats.com/hard94.html
http://www.barefeats.com/hard100.html
http://www.amug.com - reviews, incl. one on Mac Pro 2008 (I don't think they did one just on Apple's Pro RAID but used it in comparing other controllers).
I would just throw 4 WD Caviar SE16 640GB, or RE2 (when they become available). And use software, not hardware RAID. If you want RAID5/6 get an external. In fact, your idea of using 500GB drives mirrored to 1TB.... just backup instead. And while there are 500GB 7.2K, I would get the 640GB
http://eshop.macsales.com/item/Western%20Digital/WD6400AAKS/

Inexpensive, easy to use, reliable RAID USB/FW enclosure

Does anyone have any experience with RAID enclosures ?
For example, there is one by NewerTech that takes two drives and uses USB to connect to the Mac. The description claims it is compatible with OS X.
How do these things work with OS X Leopard ? Do I need to consider anything special ?
Thanks!
Oleg

You might have a look at http://www.galaxymetalgear.com/Products/3500MGBR.html for one possible solution - I have two of these in use on a couple of systems - they both work very well and are easy to set up, also have FW 400, 800 and USB.

To RAID or not to RAID, that is the question

People often ask: Should I raid my disks?
The question is simple, unfortunately the answer is not. So here I'm going to give you another guide to help you decide when a raid array is advantageous and how to go about it. Notice that this guide also applies to SSD's, with the expection of the parts about mechanical failure.
What is a RAID?
RAID is the acronym for "Redundant Array of Inexpensive Disks". The concept originated at the University of Berkely in 1987 and was intended to create large storage capacity with smaller disks without the need for very expensive and reliable disks, that were very expensive at that time, often a tenfold of smaller disks. Today prices of hard disks have fallen so much that it often is more attractive to buy a single 1 TB disk than two 500 GB disks. That is the reason that today RAID is often described as "Redundant Array of Independent Disks".
The idea behind RAID is to have a number of disks co-operate in such a way that it looks like one big disk. Note that 'Spanning' is not in any way comparable to RAID, it is just a way, like inverse partitioning, to extend the base partition to use multiple disks, without changing the method of reading and writing to that extended partition.
Why use a RAID?
Now with these lower disks prices today, why would a video editor consider a raid array? There are two reasons:
1. Redundancy (or security)
2. Performance
Notice that it can be a combination of both reasons, it is not an 'either/or' reason.
Does a video editor need RAID?
No, if the above two reasons, redundancy and performance are not relevant. Yes if either or both reasons are relevant.
Re 1. Redundancy
Every mechanical disk will eventually fail, sometimes on the first day of use, sometimes only after several years of usage. When that happens, all data on that disk are lost and the only solution is to get a new disk and recreate the data from a backup (if you have one) or through tedious and time-consuming work. If that does not bother you and you can spare the time to recreate the data that were lost, then redundancy is not an issue for you. Keep in mind that disk failures often occur at inconvenient moments, on a weekend when the shops are closed and you can't get a replacement disk, or when you have a tight deadline.
Re 2. Performance
Opponents of RAID will often say that any modern disk is fast enough for video editing and they are right, but only to a certain extent. As fill rates of disks go up, performance goes down, sometimes by 50%. As the number of disk activities on the disk go up , like accessing (reading or writing) pagefile, media cache, previews, media, project file, output file, performance goes down the drain. The more tracks you have in your project, the more strain is put on your disk. 10 tracks require 10 times the bandwidth of a single track. The more applications you have open, the more your pagefile is used. This is especially apparent on systems with limited memory.
The following chart shows how fill rates on a single disk will impact performance:
Remember that I said previously the idea behind RAID is to have a number of disks co-operate in such a way that it looks like one big disk. That means a RAID will not fill up as fast as a single disk and not experience the same performance degradation.
RAID basics
Now that we have established the reasons why people may consider RAID, let's have a look at some of the basics.
Single or Multiple?
There are three methods to configure a RAID array: mirroring, striping and parity check. These are called levels and levels are subdivided in single or multiple levels, depending on the method used. A single level RAID0 is striping only and a multiple level RAID15 is a combination of mirroring (1) and parity check (5). Multiple levels are designated by combining two single levels, like a multiple RAID10, which is a combination of single level RAID0 with a single level RAID1.
Hardware or Software?
The difference is quite simple: hardware RAID controllers have their own processor and usually their own cache. Software RAID controllers use the CPU and the RAM on the motherboard. Hardware controllers are faster but also more expensive. For RAID levels without parity check like Raid0, Raid1 and Raid10 software controllers are quite good with a fast PC.
The common Promise and Highpoint cards are all software controllers that (mis)use the CPU and RAM memory. Real hardware RAID controllers all use their own IOP (I/O Processor) and cache (ever wondered why these hardware controllers are expensive?).
There are two kinds of software RAID's. One is controlled by the BIOS/drivers (like Promise/Highpoint) and the other is solely OS dependent. The first kind can be booted from, the second one can only be accessed after the OS has started. In performance terms they do not differ significantly.
For the technically inclined: Cluster size, Block size and Chunk size
In short: Cluster size applies to the partition and Block or Stripe size applies to the array.
With a cluster size of 4 KB, data are distributed across the partition in 4 KB parts. Suppose you have a 10 KB file, three full clusters will be occupied: 4 KB - 4 KB - 2 KB. The remaining 2 KB is called slackspace and can not be used by other files. With a block size (stripe) of 64 KB, data are distributed across the array disks in 64 KB parts. Suppose you have a 200 KB file, the first part of 64 KB is located on disk A, the second 64 KB is located on disk B, the third 64 KB is located on disk C and the remaining 8 KB on disk D. Here there is no slackspace, because the block size is subdivided into clusters. When working with audio/video material a large block size is faster than smaller block size. Working with smaller files a smaller block size is preferred.
Sometimes you have an option to set 'Chunk size', depending on the controller. It is the minimal size of a data request from the controller to a disk in the array and only useful when striping is used. Suppose you have a block size of 16 KB and you want to read a 1 MB file. The controller needs to read 64 times a block of 16 KB. With a chunk size of 32 KB the first two blocks will be read from the first disk, the next two blocks from the next disk, and so on. If the chunk size is 128 KB. the first 8 blocks will be read from the first disk, the next 8 block from the second disk, etcetera. Smaller chunks are advisable with smaller filer, larger chunks are better for larger (audio/video) files.
RAID Levels
For a full explanation of various RAID levels, look here: http://www.acnc.com/04_01_00/html
What are the benefits of each RAID level for video editing and what are the risks and benefits of each level to help you achieve better redundancy and/or better performance? I will try to summarize them below.
RAID0
The Band AID of RAID. There is no redundancy! There is a risk of losing all data that is a multiplier of the number of disks in the array. A 2 disk array carries twice the risk over a single disk, a X disk array carries X times the risk of losing it all.
A RAID0 is perfectly OK for data that you will not worry about if you lose them. Like pagefile, media cache, previews or rendered files. It may be a hassle if you have media files on it, because it requires recapturing, but not the end-of-the-world. It will be disastrous for project files.
Performance wise a RAID0 is almost X times as fast as a single disk, X being the number of disks in the array.
RAID1
The RAID level for the paranoid. It gives no performance gain whatsoever. It gives you redundancy, at the cost of a disk. If you are meticulous about backups and make them all the time, RAID1 may be a better solution, because you can never forget to make a backup, you can restore instantly. Remember backups require a disk as well. This RAID1 level can only be advised for the C drive IMO if you do not have any trust in the reliability of modern-day disks. It is of no use for video editing.
RAID3
The RAID level for video editors. There is redundancy! There is only a small performance hit when rebuilding an array after a disk failure due to the dedicated parity disk. There is quite a perfomance gain achieveable, but the drawback is that it requires a hardware controller from Areca. You could do worse, but apart from it being the Rolls-Royce amongst the hardware controllers, it is expensive like the car.
Performance wise it will achieve around 85% (X-1) on reads and 60% (X-1) on writes over a single disk with X being the number of disks in the array. So with a 6 disk array in RAID3, you get around 0.85x (6-1) = 425% the performance of a single disk on reads and 300% on writes.
RAID5 & RAID6
The RAID level for non-video applications with distributed parity. This makes for a somewhat severe hit in performance in case of a disk failure. The double parity in RAID6 makes it ideal for NAS applications.
The performance gain is slightly lower than with a RAID3. RAID6 requires a dedicated hardware controller, RAID5 can be run on a software controller but the CPU overhead negates to a large extent the performance gain.
RAID10
The RAID level for paranoids in a hurry. It delivers the same redundancy as RAID 1, but since it is a multilevel RAID, combined with a RAID0, delivers twice the performance of a single disk at four times the cost, apart from the controller. The main advantage is that you can have two disk failures at the same time without losing data, but what are the chances of that happening?
RAID30, 50 & 60
Just striped arrays of RAID 3, 5 or 6 which doubles the speed while keeping redundancy at the same level.
EXTRAS
RAID level 0 is striping, RAID level 1 is mirroring and RAID levels 3, 5 & 6 are parity check methods. For parity check methods, dedicated controllers offer the possibility of defining a hot-spare disk. A hot-spare disk is an extra disk that does not belong to the array, but is instantly available to take over from a failed disk in the array. Suppose you have a 6 disk RAID3 array with a single hot-spare disk and assume one disk fails. What happens? The data on the failed disk can be reconstructed in the background, while you keep working with negligeable impact on performance, to the hot-spare. In mere minutes your system is back at the performance level you were before the disk failure. Sometime later you take out the failed drive, replace it for a new drive and define that as the new hot-spare.
As stated earlier, dedicated hardware controllers use their own IOP and their own cache instead of using the memory on the mobo. The larger the cache on the controller, the better the performance, but the main benefits of cache memory are when handling random R+W activities. For sequential activities, like with video editing it does not pay to use more than 2 GB of cache maximum.
REDUNDANCY(or security)
Not using RAID entails the risk of a drive failing and losing all data. The same applies to using RAID0 (or better said AID0), only multiplied by the number of disks in the array.
RAID1 or 10 overcomes that risk by offering a mirror, an instant backup in case of failure at high cost.
RAID3, 5 or 6 offers protection for disk failure by reconstructing the lost data in the background (1 disk for RAID3 & 5, 2 disks for RAID6) while continuing your work. This is even enhanced by the use of hot-spares (a double assurance).
PERFORMANCE
RAID0 offers the best performance increase over a single disk, followed by RAID3, then RAID5 amd finally RAID6. RAID1 does not offer any performance increase.
Hardware RAID controllers offer the best performance and the best options (like adjustable block/stripe size and hot-spares), but they are costly.
SUMMARY
If you only have 3 or 4 disks in total, forget about RAID. Set them up as individual disks, or the better alternative, get more disks for better redundancy and better performance. What does it cost today to buy an extra disk when compared to the downtime you have when a single disk fails?
If you have room for at least 4 or more disks, apart from the OS disk, consider a RAID3 if you have an Areca controller, otherwise consider a RAID5.
If you have even more disks, consider a multilevel array by striping a parity check array to form a RAID30, 50 or 60.
If you can afford the investment get an Areca controller with battery backup module (BBM) and 2 GB of cache. Avoid as much as possible the use of software raids, especially under Windows if you can.
RAID, if properly configured will give you added redundancy (or security) to protect you from disk failure while you can continue working and will give you increased performance.
Look carefully at this chart to see what a properly configured RAID can do to performance and compare it to the earlier single disk chart to see the performance difference, while taking into consideration that you can have one disks (in each array) fail at the same time without data loss:
Hope this helps in deciding whether RAID is worthwhile for you.
WARNING: If you have a power outage without a UPS, all bets are off.
A power outage can destroy the contents of all your disks if you don't have a proper UPS. A BBM may not be sufficient to help in that case.

Harm,
thanks for your comment.
Your understanding was absolutely right.
Sorry my mistake its QNAP 639 PRO, populated with 5 1TB, one is empty.
So for my understanding, in my configuration you suggest NOT to use RAID-0. Im not willing to have more drives in my workstation becouse if my projekts are finished, i archiv on QNAP or archiv on other external drive.
My only intention is to have as much speed and as much performance as possible during developing a projekt
BTW QNAP i also use as media-center in combination with Sony PS3 to run the encoded files.
For my final understanding:
C: i understand
D: i understand
E and F: does it mean, when i create a projekt on E, all my captured and project-used MPEG - files should be situated in F? Or which media in F you mean?
Following your suggestions in want to rebulid Harms-Best Vista64-Benchmark comp to reach maximum speed and performance. Can i use in general the those hardware components (exept so many HD drives and exept Areca raid controller ) in my drive configuration C to F. Or would you suggest some changings in my situation?

Raid cards for mac pro 2.66

i would like to set up a hardware card for my os as raid 0
(2 10,000 rpm hard drives)
and a hardware raid 1 for my data.(same/separate card ??)
are there any sudgestions on makes and models and compatability?
i am aware of the software raids provided by the os, i've heard they are not as reliable and fast as the harware solution, agree, disagree???

Yeah they say the software raid is good and I can't say first hand but I have heard good reports. In general I prefer hardware RAID but i setup server not clients so. Was using acard.com stuff for a bit but there offerings have gone down on the mac side. My current card of choice is Highpoint's Rocket RAID.
http://www.highpoint-tech.com/
Card works good and drivers all appear to be up-to-date with Intel based Mac's now. Nice web-GUI to the Raid controller. My only complaint could be OS related as opposed to driver but the Hot-Swap won't work right. In order for me to swap i need to drop the drives from the server and pull them. (alarms alarms, lol) Then put my swaps in. Seems the release call from the web-GUI does not kick the drive out right or the Mac OS won't let go of them even after un-mounting.

General HELP for RAID and HOME NETWORK... I'm a bit lost :(

First off, I'm sorry about the long post but I just wanted to ask everything at once since I don't know what effects what?
Over the past years I've had a MBP and have always added Western Digital Mybook drives whenever I needed storage. One of clicked and died this past year and I lost some data since I was "MANUALLY" backing up. Since then I've tried to read about RAID, NAS, and DROBO type devices.
I recently bought a Mac Pro 2008 edition because I needed more speed. I mainly edit wedding photos in Lightroom but also come from a heavy motion graphics background and do some After Effects projects from time to time.
Here's a list of my current setup and what I'm hoping to achieve but I'm in over my head of what to do???
1 Mac Pro (2008 edition) - I'm considering setting up 4 1TB harddrives inside that are mirrored. I was looking at the Caviar Black or Hitachi drives...
2. I have two Airport Extreme Base Stations for my home network. (One is plugged into my Mac Pro and the other is near my Vizio LCD and Xbox 360. I've been toying around with sharing iPhoto slideshows (which I really like the idea of) The problem is that it seems really slow for video and hiccups on the stills sometimes. It doesn't seem to make a difference if it's pulling it from the Mac Pro or from a USB drive attached directly to my Airport Extreme. How do I speed this up? Is it always going to be faster to stream from the Mac Pro over ethernet cable than a harddrive plugged in through USB?
3. A few RAID and NAS solutions I've been looking at are the following but I don't really understand what I get with an external device vs an internal? I also don't know which is BETTER? for easy reliable backup.
http://firmtek.stores.yahoo.net/sata5pm2se2.html
http://www.dlink.com/products/?sec=0&pid=667
http://www.qnap.com/prodetail_feature.asp?pid=110
http://eshop.macsales.com/shop/hard-.../RAID/Desktop/
http://www.synology.com/enu/products/CS407/index.php
4. I've been reading mixed reviews about the Drobo but don't quite understand if it's a better solution then setting up a mirror INSIDE my Mac Pro. I DO NOT want to buy a $900 raid card for the Mac Pro though. Do most people choose the Drobo because they only have laptops? Should I only consider building something inside my Mac Pro?
5. I was considering Chonosync for backing up 3rd level backups
6. I just bought a Blu-Ray drive for 4th level backups that I can send off site.
7. I have all these other Mybooks. Two of them are mirrored but only one is a 1TBx2 Sata drive. The rest are IDE. I guess I'll just use these for misc things? Maybe just plug one into the Xbox for watching movies?
8. My neighbor down the hall has a similar setup and is using a Mac Mini to stream things (through Front Row) like Hulu and videos another room to his TV. Mine doesn't seem to stream fast enough. Since I have the MBP that I will use rarely since I got my desktop I was considering using that instead of Apple TV or a Mac Mini but it's too slow? Maybe I set it up wrong?
PLEASE HELP? I don't know what I'm doing.

A few RAID and NAS solutions I've been looking at are the following but I don't really understand what I get with an external device vs an internal? I also don't know which is BETTER? for easy reliable backup.
Hi,
For backup, video work, photography and expanding the Mac Pro storage capability the FirmTek SeriTek/5PM would be my choice. The bundle that you pointed to will work if 130MB/sec. is fastest enogh for your needs. The card is only $70 in the bundle which makes it a nice deal.
http://firmtek.stores.yahoo.net/sata5pm2se2.html
If you want 200MB/sec, performance I would go with the Sonnet Tempo E4P or the HighPoint RR 2314 if you desire RAID 5 redundancy.
http://www.amug.org/amug-web/html/amug/reviews/articles/sonnet/mac-pro/
http://www.amug.org/amug-web/html/amug/reviews/articles/highpoint/2314/
Trying to use NAS via the network will be 3-7x slower than the SeriTek/5PM. The SeriTek/5PM is a much better choice for backup, video and photography. NAS is good for low energy, always on, low use server needs. However, you can simply turn Mac OS X file sharing on and the Mac Pro will provide performance faster than any NAS.
Drobo - Why do people even consider this option?
The performance is USB speed even with a FW800 connection.
Users have reported losing data with firmware updates.
And the unit is one of the most expensive, slow performing options available. I cannot image ever wanting a Drobo
Backup Software:
I like SuperDuper. I also like using the "Restore" tab in Disk Utility to clone one disk to another. The key to good backup is to keep it simple and regular.
MyBook - NOT
If your storage needs exceed more than a single FireWire backup disk you really need to go with eSATA. The SeriTek/5PM and the Mac Pro combination provides virtually unlimited storage capabilities as the tray system allows new hard disk sets to be easily loaded or dismounted.
Have fun!

Simplest/most reliable setup for 2 mini's+ext HD+backup+printer?

Hello and a happy 2009 to everyone,
I'm a recent switcher (replaced one PC with a mini). Using it for internet/email and getting to grips with OpenOffice 3.0; transferred photos and music onto an ext HD and using them with iTunes and iPhoto (and trying out Acorn for editing the photos). Very happy so far !
Next step is replacing our other PC with another mini (though I may wait to see if they'll be updated soon) and getting the two mini's linked up and sharing a (non-network) printer, the internet connection (through the ADSL modem provided by the internet provider; it has WiFi and 2 ethernet sockets), the ext HD (with the photos and music files), and a second ext HD (to be purchased, RAID?) for backing up the two mini's and the first ext HD. As my wife and I would have/use each our 'own' mini and hence keep our own mail and bookmarks, there won't be a need to synchronize anything. However, there would be the need to share documents; in fact, we'd prefer to only have one home folder, but I guess that'll difficult/impossible with two machines and thus two OS running.
As I have no experience whatsoever with even the simplest of networks, I have a few (rather basic) questions:
* What's the best/simplest/most reliable way to achieve the above?
E.g.: linking the two mini's thru an ethernet (gigabit) connection and fully sharing everything, attaching the printer and one ext HD to one mini and the other ext HD to the other mini, and both mini's wirelessly to the ADSL modem (which we'd really rather prefer to do thru ethernet, but the mini's only have one ethernet socket each…)? Advantage(?) would/could be that both ext HD's could be FW rather than USB. Would backing up on one ext HD (thru Time Machine), of both internal HD's and the other ext HD work that way?
Or should we get an AEBS (or another router) and connect both mini's (which will be in the same room, not far from each other and not far from the ADSL modem and the printer either) as well as the ADSL modem to it thru ethernet and, thru an USB-hub, the ext HD's (thru AirDisk) and the printer as well?
Or a combination of the above?
Or in a different way altogether?
Are there any other things that I have to take into account?
Any response highly appreciated!

Steve, thanks for your input!
In the meantime I've found out that my ADSL modem is also a NAT router, but 'only' 10/100 Mb/s, so I was wondering whether I get/do/make what I want to achieve a bit cheaper/simpler?
E.g. thru a Gigabit switch (rather than an AEBS) to which I connect the 2 Mini's as well as the modem/router, and the printer and external HD's directly to the mini's?
Some Qs:
* Would a Mini-to-Mini connection thru a (Gigabit) switch work better/faster than plugging both mini's into the (10/100) modem/router?
* Would in either scenario both mini's have to be on (and not 'just' in sleep mode) to be able to share the printer and the external HD's?

Mac OSX 10.4.8 Update Breaks Raid Striping -- System will no longer boot

Hi,
I'm a newbie from the PC world with a Mac Pro. For the last 8 hours I've been trying to get a Raid-0 configuration to work with no success.
The Raid array constructs ok and the system boots. Once that's done the Software Update screen arrives and I would select install all... then the machine would not boot. I get a Grey Shade like affect and the message to power off and restart. Powering off does nothing.
So I started again for the Nth time and added each Software Update individually. All loaded and rebooted successfully until the 10.4.8 Update.
As soon as that loads, installs and restarts the machine will not boot.
I called Apple's Tech Support and they told me they do NOT support RAID on this machine. I said what are you talking about. They put me on hold talked to a supervisor and came back with the same story. I just don't get it...
So anyone have any insight and advice on why the update breaks my Raid-0? What can I do to get over the problem (I'd like to have the RAID...)?
Thanks for the assistance.
Mac Pro Mac OS X (10.4.8)

Yes, you needed an emergency boot drive anyway to repair your RAID boot drive. Just use the same one in addition to a working clone or backup of your regular system.
Apple made it easy to install or update security updates and system updates from an alternate drive (but you will have to use the stand-alone (combo preferably) updaters instead - which many use already as normal part of upgrades for years now (they seem more useful and reliable).
My preference is a dedicated boot drive with OS and apps and minimal home directory - no media files - and fast, like 10K Raptor. I use RAID for my home directory so it isn't on the boot drive for years to improve performance and keep the OS separate. Never a problem and nice mix.

DIY Fusion Drive and RAID 5

Hi everyone!
I have spent several hours by reading various forums but haven’t found any definitive answers.
I have a 12 Core Mac Pro with the following setup: one 1TB SATA hard drive that carries the system and applications. For the files and storage there are three 2TB SATA drives in RAID 5 controlled by Apple RAID card. I am going to install a 512 GB Samsung 840 Pro SSD drive in the optical bay and have initially planned to use it just for the system and applications, but am curious if the following is possible.
1) Is it possible to combine the RAID 5 array with the SSD and create a Fusion drive?
2) If yes, will it retain all the features of the RAID 5?
3) Should TRIM be enabled?
Thank you in advance!

TRIM directly addresses the shortcomings of having only garbage collection available. SSD controller manufacturers and designers (including SandForce, the controller manufacturer for OWC's SSDs), recommends that TRIM be used with their products. So does Samsung.
For example, here's a 2011 article from OWC describing how you don't need TRIM on their SSDs and how it can in fact hurt performance or reliability.
That article has been discussed here on MacInTouch before. In my opinion it's bad advice, and inaccurate in some of its assertions. It also ignores the recommendation made by SandForce to use TRIM with their SSD controllers. But even if one were to take that article at face value, applying that advice to SSDs other than OWC's makes little sense.
The reason I'm advising against TRIM is simply that it's yet another driver-level modification of the OS, and these always carry potential risk (as all the folks with WD hard drives who lost data can attest to).
Apples and oranges comparison, for a variety of reasons. The short of it is that TRIM is supported natively in all recent versions of OS X. The tools used to enable it for third party SSDs do not add a new kernel extension; they change the setting to allow Apple's native TRIM implementation to be used with SSDs other than those factory installed by Apple.
This shows that the 840s do work slightly better with TRIM than without, but the differences are (in my opinion) trivial, a 9% increase at best.
One of the major reasons for the skepticism that exists about TRIM is that so many people, the authors of both articles you linked to included, don't understand it.
TRIM is not, strictly speaking, a performance-enhancement technology -- though it is plainly obvious that most people think it is.
Though it can, in many circumstances, improve performance, there are also circumstances under which it will provide little or no noticeable benefit. Not coincidentally, a new SSD tested fresh out of the factory packaging is unlikely to show much (if any) benefit. Or rather, TRIM is providing a real benefit for new SSDs, but that benefit doesn't become measurable in terms of benchmark performance testing until every memory cell in the SSD -- including many gigabytes of cells hidden from visibility by the SSD controller -- have been written to at least once. Writing 128 GB of files to an SSD with a nominal capacity of 128 GB won't do it, as there are several gigabytes (exact number varies depending on the model) still unwritten.
Under real-world use conditions, having TRIM disabled means eventually having noticeable write performance degradation due to write amplification. It is far greater than "9%" -- it can be a 50% or greater drop in write performance, depending on various factors. Defining "eventually" is difficult because it depends on how the SSD is used. But given enough time and write cycles, it can happen to all SSDs used without TRIM, no matter how sophisticated their garbage collection algorithms are.
Under those same real-world use conditions, having TRIM enabled means that the SSD should almost never reach a state of having noticeable write performance degradation, as it should almost never get into a state where write amplification is happening.
I will concede that it is possible to design a lab test in such a way as to defeat the benefits provided by TRIM, but such tests do not reflect any real-world usage scenario I can imagine. Furthermore, those same contrived tests would put an un-TRIMmed drive into an equally-addled state even more quickly.
I would suggest reading through the rather lengthy previous discussions about TRIM. Here are a couple of my past posts that are most relevant to the current discussion:
A description of what TRIM is here.
I addressed some of OWC Larry's comments about TRIM use with OWC/SandForce SSDs here.
http://www.macintouch.com/readerreports/harddrives/index.html#d09dec2013

Advice on RAID and backup of new server in CAD office

Hi, I work for an architects firm and we're looking to purchase a new server.
Our current situation:
• Dozen workstations running Leopard, on a gigabit network
• Server running Leopard Server (Standard setup), with one 250GB ATA hard drive (17GB space spare)
• Data files are backed up and taken off site each day with a triple rotation of external hard drives, using Retrospect.
• The server hard drive is cloned to an external drive each week, which stays on site, using SuperDuper.
• User accounts from workstations are all backed up to an external drive, which also stays on site, using Retrospect.
• And I've been trialing Time Machine, backing up the data to an external hard drive, but I can't see this replacing Restrospect backup as Time Machine doesn't compress the files.
To the future:
• What sort of RAID setup should we go for in a new Mac Pro server?
• I'd like to throw it all into performance but I'm thinking we should probably use a RAID to replace our SuperDuper clone from above.
• When you have mirrored drives presumably if one fails the other one just carries on doing all the work by itself?
• Should we run the system on two mirrored drives and the data on the other two? Or if I'm looking for more performance would I be better having 3 mirrored drives for the data and one for the system? Is this even possible?
• Is it possible to get the smaller 73GB SAS drives for the Mac Pros? It seems you can only get the 300GB ones, which are £500 a pop!

Keep in mind that mirrored RAIDs require two similar drives preferably the same make and model. A mirrored RAID only provides drive failure protection, it does not provide data redundancy. If you need a backup then you need two mirrored RAIDs using one to backup the other. This is also true of striped RAIDs which only provide increased storage but provide no protection against drive failure nor provide data redundancy.
These factors should be taken into account when planning your setup.
Personally, I would not recommend using Time Machine. Aside from being fairly basic as a backup utility it is not sufficiently reliable in my opinion for your situation. Retrospect is a much better choice.

Backup solutions w/RAID or redundancy (NAS, RAID, DIY File server)

Hi all, I need a place to bounce my ideas off of. Here goes:
I have been doing a lot of reading, since I was considering adding an NAS solution for my home network. My data consists mainly of videos (TVs and movies) and pictures (many many years worth).
Anyways, out of the box solutions seemed a bit too pricy and the RAID not that spectacular unless you're willing to spend, so I began looking at building my own fileserver, with a hardware/software RAID solution. That was a bit better bang for the buck, but I still had one nagging concern.
I've played around with RAID before, and I realized that with mirroring (the only RAID option I was really considering), was that it relied on the RAID controller. I couldn't just take a hard drive, remove it physically from the array, and have my information accessible when plugging it into another computer.
What happens in a few years if your RAID controller dies and you can't find the exact same one? Your array will always be dependent on that controller and I really don't like that feeling. I'd rather have the option of taking a drive, plugging it in another computer, rather than needing to move the whole array (RAID, NAS, DIY file server) around. That means quicker access to my information or the ability to take it with me anywhere I go, on a moment's notice.
The least costly solution I have come up with, for data that doesn't change all that much, is to have two huge drives (1 TB) on a computer, either one or both connected via eSATA. Just remember to ghost/copy the main drive once in a while, and keep the 'backup' drive detached (preferably located in a fire-proof safe) and back it up once in a while, on a regular basis).
Sorry for the long post, but how does that sound, for a cheap, reliable backup solution, for data that doesn't get updated too frequently and for ease of access and use?

Hi BGBG;
For what you are attempting to do, RAID is not the best solution. The reason I say this is because RAID 1 is only capable of protection from disk failure. It is not a valid backup solution.
I think that your last solution of using eSATA and a copy is the best. My only addition to your proposal would be a third disk. That way when you move the backup disk into storage you could replace it with the third one. In this way you could use SuperDuper to periodically backup between two disks.
Allan

Best option for initial setup of HD's on Xserve (possible RAID)

I'm just about to set up a new network in a new office and have an Xserve with 3 HD's 2x700GB and 1x500GB drive.
Now i have a fair bit of experience with the server itself, however i have zero experience with RAID.
I would like to start automatic backups of the OS (which i do already in a round about way). And have several share points for users network homes and data.
Does anyone have any suggestions of how to setup the HD's themselves, should i RAID? what would be the best option? etc etc etc.
All suggestions are very welcome and appreciated.
Thanks
Steven

No one can answer your question - at least not without more information.
When deciding disk layout you need to factor things like how much usable disk space you need - in this case for users' data. Are the users home directories on the server, or do they just upload files to the server for storage/backup?
What's the intensity of the data? Is reliability or performance more important? Would you pull your hair out if you lost a single file? a day's work? a week's work?
How much downtime could you tolerate if the server crashed?
These questions (and probably more) are important because it helps focus on the needs. For example, if the integrity of the data is more important than uptime you could mirror the two 700 GB drives for the user data and install the OS on the single 1TB drive. Of course this leaves you (slightly) vulnerable to a problem on the OS disk and you could be offline for hours if that disk failed. However, your user data would be mirrored and likely protected from disk failure.
On the other hand, if the uptime of the server is more important, you might opt to install the OS on the 700GB mirror, using the 1TB for user data, relying on backups to restore this disk if it fails.
Or, you might decide to put everything (OS and data) on the 700GB mirror, using the 1TB as the backup destination.
On the other hand you might determine that you need 1TB of user storage space, in which case you either need to use the 1TB for user data, or you need to stripe the two 700GB drives into a 1.4TB array, but then that array has no redundancy and the loss of a single disk will result in the loss of all data.
So, as I said, there is no one single answer to your question. You'll need to balance storage capacity and redundancy to find the best match for you.

Lost RAID 5 Array...

I have, er... had, a RAID 5 array comprised of six 180GB Apple Drive modules. The Xserve RAID had cache battery backups installed and was on a UPS, but I had disabled the drive cache for all drives quite some time ago as I wasn't sure how reliable the cache battery backups were anymore. This wasn't performance intensive, it was mainly a second repository for backups.
Unfortunately, I came in to work Friday morning to find the RAID powered down (in standby mode). I powered it back up (it was still shown as being mounted on the file server which is running Mac OS X Server 10.3.9, but the volume was empty and listed the correct amount free). Of course, that didn't bring up and data, so I rebooted both the Xserve and the Xserve RAID.
Disk Utility showed no array and neither did RAID Admin.
No luck. I've swapped controllers, upgraded the controllers to the latest firmware. Nothing.
I've searched through this discussion forum's history and tried everything I ran across (power up order of the Xserve and Xserve RAID, powering down the RAID, pulling the cache battery backups, and waiting five minutes, the "Recognize Array" feature in RAID Admin, DiskWarrior, etc). Nada.
Any additional suggestions? Most of the "lost array" discussions are from last year, so I'm surprised this happened to me (maybe because the Xserve RAID was still running old firmware). Also, what is the "Recognize Array" feature really for if it won't allow you to select drives to try to recognize?
I still have not tracked down how the RAID was powered down (it's in a private server room and I'm the only admin that manages the servers in there).
Thanks for any help or insight anyone can provide.
Dual 1.33Ghz Xserve G4 w/Xserve RAID Mac OS X (10.3.9)

Shane: Yes. I tried Disk Warrior, but as there's no RAID Set, there's no volume even available to try to repair.
Dave: Unfortunately, I came to the same conclusion that you have. Very odd that this issue seems so prevalent on the pre-1.5 firmware.
I've kissed my data goodbye (it was all backups, so not vital, but I would have liked to keep it), recreated the set and we'll see how it goes with the new firmware. I'm also setting up a second RAID to mirror the data to for more redundancy in the future.
Andrew: I'm sorry to hear you're having the same issue, but glad you've got a backup. This issue definitely is a big time waster in the least.
Unfortunately, it appears (from my experience, unless I too was missing some undocumented modifier key combo) that you have to have atleast one drive that still remembers what set it belongs to in order to use the "Recognize Array" feature.
From past discussions, I've gained that Apple can actually recover/rebuild the RAID set from drives sent to them, but in my case it wasn't worth spending any additional amount of money on getting the RAID set back up (my time was costly enough).

I want to add another hard drive to my exsisting RAID 0 setup - how can i do this?

Hi all, wonder if somebopdy can help me
I have my computer setup as follows:
1 x SSD - used for my O/S - windows 7 ultimate 64bit
2 x 1 TB hard drives - WD black series in a RAID 0 arrar
Now Im slowly but surely running out of space on the RAID ( the two hard drives) so im thinking about purchasing 2 x more of these exact same hard-drives to add to the RAID but iv never done this before and obviously I cannot lose any of my data currently
saved on this RAID - as iv deleted everything I don't use or want
what is the best way to back all my data up and how would I add 2 x new hard drives to my RAID 0 so that it will include 4 x 1 tb hard drives in total
thank you hope somebody can help

Hi,
You have to know that with a RAID 0 (striped set), if any drive in the array fails for any reason, you will loose all data on the volume. In this case, the more drives you add, the greater the chance for failure--with increased I/O.
Being you already have a RAID 0 setup with two drives, you cannot just break the stripe--you will loose all data if not backed up.
To effectively add another drive to your RAID 0 implementation, you will have backup your machine--making an image is the best option--break the array, add the drive and then restore your image.
About how to extend the raid 0, you may need some third-party tool to complete. Here is some references for you:
http://www.partition-tool.com/resource/extend-raid-software.htm
http://www.partitionwizard.com/resizepartition/extend-raid-0-partition-windows.html
Please Note: The third-party product discussed here is manufactured by a company that is independent of Microsoft. We make no warranty, implied or otherwise, regarding this product's performance
or reliability.
Please Note: Since the website is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.
Please remember to mark the replies as answers if they help, and unmark the answers if they provide no help. If you have feedback for TechNet Support, contact [email protected]

I have some queries usage of RAID 1 on OSX

Hi there
I apologise for the length of this question, but there's quite a bit of relevant data. I work in a small typesetting company (<10 employees) and since a HDD failed on an old G4 iMac that we used as a data archive we have learnt that without our data we are nothing. I have now been asked to implement a more reliable back up/recovery system (with minimum downtime) that increases the 'safety' of our customer's data. Rebuilding the archive took days to sort out and because the archive was constantly accessed by our production macs and a couple of PC as well, it hit us hard.
We are looking into turning an old G5 Powermac (1.8Gz single processor 2.5Gb RAM) into a RAID 1 (mirrored) system with 2 x 1TB SATA drives using Disk Utility. We would have this to protect against one HD failing and losing customers' data. I understand that this is not a back up system, just something that would protect customer's data should a drive critically fail. I have some queries regarding how this works though.
1) How much (if any) maintenance is required on a RAID system? None of use are IT specialists - just typesetters with a bit of technical knowledge.
2) Is a mirrored RAID system reliable, considering multiple people are reading/writing to the machine throughout the day?
3) Do RAID 1 systems handle being accessed by different OSs (WinXP, Win7, OSX 10.4–10.6) well?
4) Am I right in thinking that OSX would see the two drives as separate volumes?
5) Should one drive fail and need to be 'rebuilt' via Disk Utility, can users still access the one working HD, or do you need to replace the failed HD and rebuild before anyone can access the data again?
6) Considering Question 4 above, do we need to have a 3rd 'spare' 1TB Drive just in case?
7) We are looking into a two-week backup system, backing up all the customers data on a daily basis, with the previous week's disk being stored off-site. We were initially looking into either Carbon Copy Cloner or RSync the copy data to external HDDs. How would you rate Time Machine against these products, and does anyone have any experience using these solutions with RAIDed Macs?
8) Is there any 'downside' to RAID 1 systems?
I know this is a lot of questions, but I really don't want to start down this route unless I understand it better first.
Many thanks in advance for your contributions!

Mac_fool wrote:
Thanks for your reply!
So, in order to have a RAID visible and accessible by multiple OSs, and to eliminate downtime during rebuilds, a hardware RAID would be necessary.
Well, not quite. When you create a RAID in Disk Utility, the volume only exists as a MacOS X file system. Your Mac can share that volume to any other machines or operating systems.
What I mean by a hardware RAID is some box whose output port is eSATA or USB or some other non-network storage port. On such a device, the logic to create the file system is inside the box. Any machine that is connected to it would see only a single disk. You would still have to ensure that different operating systems could understand whatever file system you were using (HFS+, FAT, NTFS, etc), but that is the same as if you had a non-RAID external drive.
I have one of those. It is an older FireWire 800 drive that has two 300 GB disks inside. To any machine I connect that to, it appears as a single 600 GB drive. This particular device isn't designed for mirroring, however. If it were, it would only show itself as a 300 GB hard drive and I would have the capability to easily swap out the internal mechanisms when they fail.
By 'hardware RAID', do you mean inserting a RAID controller card inside the G5, or a separate storage device, such as a RAIDed NAS-type-thing? Would an ethernet-connected NAS be slower to access than a G5 with internal SATA? Am I right in thinking that those RAID-ready NAS devices cannot be partitioned at all?
I qualified the above to explicity avoid NAS devices just to simplify things.
I'm not familiar with RAID controller cards. My guess is that they are just a cheaper alternative to an external RAID device. It would allow you to plug your own hard drives into the controller card and create the RAID. They would certainly provide higher performance that if the operating system were handling the details.
If you want to have a RAID for data reliablity, you really need an external, self-contained device that has a standard hardware storage port you could plug into any machine. It would look and act just like any other external hard drive. But if a drive failed, a light would flash on the box and you could just pull out the failed hard drive and replace it with a new one. You wouldn't even need to power anything down.
For both RAID controller cards and stand-alone boxes, you may or may not need additional software to partition and format the drive. It depends on the model and manufacturer.
Such a device could also be NAS. In this case, it would have an ethernet interface instead (or in addition). The difference is that such an interface would almost always be slower than a true storage interface like Firewire or USB. Plus, you would usually have to let the box itself handle its partitioning and formatting. Since it is designed to be a networked drive, you don't need another machine to be the server. It is its own server. This is useful in those cases where you don't want/need a dedicated server. The downside is that it probably runs some lowest-common denominator Windows networking for maximum compatibility. Foreign, networked filesystems are always going to be more flaky. Some software may not work. Some OS upgrade may give you hassles.
To be honest, I'm no expert on RAIDs. In such situations, I usually just defer to people I know are experts. So, just buy the amount one of these: (http://eshop.macsales.com/shop/hard-drives/RAID/Desktop/), plug it in, and go. I suggest RAID 5.

RAID 1 Reliablity

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