Building a Raid-0 with two out of four internal drives?

Hello everyone
I have four drives in my MacPro:
1) OS+Apps
2) Virtualization
3) iTunes
4) empty
My iTunes library fills drive 3 and I am close to having a full drive.
I would like to 'span' my iTunes library over to drive 4 and was thinking about building a Raid-0 on drives 3) and 4).
Can I do this without any additonal software and hardware?
Do I simply do that in Disk Utility?
Can you foresee any limitations to that setup (except for fault tolerance)?
I assume performance is also sufficient as after all it is only for iTunes.
I am not worried about drive crashes as I can back-up the spanned drives externally
Any thoughts?
Thanks in advance

Quick follow-up information from the disk utility help menu:
"Using several disks as a single volume with a concatenated RAID set
If you need to set up two or more disks or volumes to work together as a single, large volume, you can create a concatenated RAID set. You can even increase the size of a concatenated disk set after it's been created by dragging more disks to it in Disk Utility. This RAID set is helpful if you have a file, such as a database, that's larger than any of the disks you have. Or you may need to create a mirrored or striped RAID set with one large disk and two smaller disks.
If you booted your computer from a disk that has multiple partitions, you cannot create a RAID set that contains partitions from your boot disk. To create a RAID disk that contains partitions from that disk, you must boot your computer from another disk or the Mac OS X Install disk first.
You cannot remove individual disks from a concatenated disk set."
So it seems I can add disks whenever I want but once added I can't remove them...

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Which is better, Raid 0 with two hdds or 1 ssd?

Hi,
I have a macbook pro Mid 2010 with two open hard drive bays (thanks to the mce optibay.) I was wondering if it would be better to put two caviar black hard drives in raid 0 on my macbook pro, or have one vertex 2 drive as a boot/applications drive and another data drive.
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I understood what the hard-drive-in-optibay meant. Regardless, it's still two platter-based hard drives versus an SSD. An SSD will be faster in your situation. If you had a lot of platter-drives in RAID0 and you had some sort of hardware based RAID controller with battery-backed cache, then maybe, possible, potentially, that (really expensive) platter-based RAID0 could be as fast as a SSD. You don't have that and can't put that in a notebook, so it ain't gonna happen for you.
Now add to the mix, the fact that RAID0 will lose data if any one of the drives in the array fails. You have two drives in RAID0 versus one drive in a non-RAID. The RAID is twice as likely to have a drive failure just because you have more drives. If you made the RAID from two SSD drives, which are more reliable than platter-based drives, then you're got something interesting. But you're still twice as likely to have a SSD-RAID0 array failure compared to a single non-RAID SSD. (And more than twice if it's platter-based drives in the RAID0 versus a single non-RAID SSD.) So it's up to you to determing how much risk you are willing to take...and how much you can afford.
Also note that some Macbook and Macbook Pro models have slower performance on the SATA port for the optical drive. (One assumes Apple tried to save a few dollars and put in a older, slower SATA controller for the optical drive.) I don't know exactly which models but if yours is one of those, then you may get uneven performance on your RAID0. Whether that is noticable or acceptable to you, will depend on a lot of things that you won't know until you try. (e.g.: model of drive, apps you're using.)
And it's good that "backup is easy for you." With RAID0 for the boot volume, you're that much more likely to have a failed boot volume. (IOW, can't boot the Mac at all, which means you'll be using that easily made backup a lot. ) Ideally, workstations that used RAID0 used them for the data, not for the OS. For example, in video editing, the scratch disk needs to be fast, but could be RAID0 because you "threw away" whatever was on the scratch disk after you were done editing, and presumably saved/copied the final edited product to another archival drive. But the OS was on a typical single drive non-RAID (or a RAID1 or RAID5 if necessary,) not on a single RAID0 array for both OS and data.
In your situation, you can't separate the OS and data onto separate RAID arrays, so in general, RAID0 is NOT what you want, regardless of whether you use SSDs or platter-based hard drives. But again, only you can determine how much risk and cost you're willing to gamble with.

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Hi,
I got a 2 TB Seagate Barracuda, which I am looking to mirror in a RAID-1 set-up. Now, since the space is filling rather fast, I suspect I'll have to keep adding disks to this machine in the future. So, I have a interest in changing to some low power (since its always on) drives.
So, I'm thinking of making the second disk a 2 TB Seagate NAS drive (and then use NAS drives from this point on), which is a fair bit slower than the main drive. Personally, I wouldn't expect this to be a problem at all, but I thought it would be best to check with others first though
Have anybody here tried running a RAID-1 where one disk is considerably slower than the other? Will this give any issues (other than the speed being limited by the slower disk)?

WonderWoofy wrote:
The speed will certainly be limited by the slowest device, as you mentioned, but what I am confused about is what you expect to achieve by continually adding drives to a RAID-1? At some point, do you plan on changing the RAID level? Because RAID-1 is mirroring. If you add another drive, you will not get more space, you will just get another copy of your data... and another... and another.
I'm not sure that btrfs would be any easier in this case, as the mdadm tools are pretty robust and certainly allow for adding and removing drives. But if you use btrfs it might actually be beneficial if you are set on keeping a RAID-1 type setup. This is because btrfs' raid levels are not quite like traditional raid. If you put your btrfs array in a RAID-1 setup with two disks, it is no different. But when you add another disk, it will continue to keep just two copies. So if you have a total of four disks, then it will still be only two copies of any given data, meaning that you will end up with twice the space of the two disk RAID-1.
Maybe you are thinking of a different RAID level altogether? If speed is not the issue but you care about redundancy and fault tolerance, then you might want to look into RAID-5 or RAID-6, though these require quite a few disks.
Ello',
I'm continuously going to be adding drivers to the machine, not to the same raid-1 array. My plan is once space gets tight, I'll add another disk and bump it up to raid-5

Does Time Machine work with two or more back up drives?

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Any help would be more then welcomed as I did something stupid and need a bit of help to fix it please.
Had an issue today on my Mac Pro (2.8, Quad 5.1). All was running fine until I went to update a piece of 3rd party software (Fetch). After the download I went to drag new version into my apps folder and was told I didn't have permission to instal the app.
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Today was the first time I have had access denied for my home folder when working from same system. Not thinking and while on the phone to someone (this is where I did the stupid part), I opened the info on my boot (startup) drive and decided to add both of my user accounts and change permissions for each in addition to the system, admin and everyone that was already there. This was done while working from it directly and then set options to "apply to enclosed items". Yea, smart I know.
About 20 minutes passed and then it told me that it didn't like any of my system extensions. I was forced to do a restart and got the spinning wheel for about 30 minutes. Had to do a force quit and open in single user. Applejack wouldn't help at all, nothing. Had to then open cd drive through terminal just to get systems disk inside.
Restarted from systems disk and tried a simple disk utility repair. System restarted fine but I noticed that I was then locked out of all of my additional internal drives, iDisk included (padlock shown on all drive icons excluding my Boot/Startup drive). Tried opening info on the various drives with apple i option and "permissions denied" popped up each time.
I then took the step to restore from time machine. Set my restore selection to about 2 hours before I became an idiot. After it was finished I restarted the system hoping that would clear up my mistake but same thing, still locked out of all of my drives aside from boot/startup drive.
All user accounts that I have added to the boot drive are still showing, I have yet to try and remove them... Figured I would ask for help before I messed it up any further. Spoke to apple care and they have advised me to do what I have done so far.
Aside from an erase and instal, what steps should I take from this point? Will removing the added accounts clear up the issue?
Also, any idea as to why I was refused permissions to begin with...?
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Raid 1 with two external drives

Hi Everyone,
I've been searching for some answers on this and havent quite found what ive been looking for so i figured id just ask. I have two identical 1tb g-drives daisy chained and hooked up to my imac via Firewire 800. I want to make one of the drives raid 1 to mirror all the information on the other. What is the best way to go about doing this?
I was also wondering would it be better just to have time machine do backups of one drive onto the other? any advantages/disadvantages to either method?
Thanks in advance everyone!
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scotty morrison wrote:
These drives will be used to store Masters and dailies from photo and video shoots and well as the final edits from those shoots, so id qualify them as "mission critical".
Instead of "making" your own RAID1 array, you may want to investigate some "turn-key" RAID solutions. For example [this one at Macsales|http://eshop.macsales.com/shop/Mercury-EliteAL-Pro-RAID]. (That's just one RAID1 turn-key unit that Macsales has.)
Since you mention video, perhaps even consider RAID5 for more capacity, or RAID10 pr RAID0+1 for higher speeds. RAID0 would be good for the edits "scratch space", but not for any "real" storage. Thus the use of RAID10 or 0+1. (If you really want to get the max performance, do some research on the differences between 10 & 0+1.)
...Im now thinking however that i should have my masters in raid1 and on separate drives have my live edits being backed up by time machine as they change. Would this be a good thing to do?
Again, RAID1 is not a backup, so regardless of where you have the "masters", they should be backed up. With the backup, you can then recover from a loss of a drive, it will just be a little more time to get running again compared to RAID1. Thus the "need" for RAID1 is debatable for the masters and final edits, etc.
Also realize that RAID1 & RAID5 generally have slower performance than an individual drive (or RAID0) due to the overhead of writing the mirror or parity info. In many "workstations", they have a individual drive to boot from, then a RAID0 array for the editing "scratch space", and the final version of the file on some other storage. (i.e.: RAID5 SAN.)
Be careful with reliance on Time Machine for backups. Time Machine is good, but sometimes Time Machine can't backup files that are in use. (e.g.: [iPhoto|http://support.apple.com/kb/HT4116].) This is true of most backup systems unless you get some really expensive software so for something you're considering "mission critical" like these video files, I'd be looking at an additional backup system. (Even something as lowly as manually copying files to an external hard drive or an Automator workflow.)
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Sorry but i think this is a very basic question.
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Building a Raid-0 with two out of four internal drives?

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