IMac sleeps even when disk activity is occurring - Mavericks

Hi,
I have had this problem for awhile, but was hoping a software update would have fixed the problem (but hasn't).
I have an 2011 iMac running Mavericks and I have noticed that the sleep function does not behave as expected.
I often have my iMac copy files between two external drives or perform backups overnight, but have found that my iMac will go to sleep in the middle of the process. I have my Energy Saver settings set so that my iMac goes to sleep after 15 minutes and will try to put the hard drives to sleep where possible, however my iMac should not go to sleep if disk activity is happening.
I find that when I wake up in the morning, my file transfers have been paused and only recommence once the IMac is woken. This is the same with my CarbonCopyClone, the backup is paused but restarts when the iMac wakes.
It used to be that these functions could happen overnight and my iMac would only sleep once they were completed.
My workaround has been to keep my iMac awake using the Caffeine Application, but this is not ideal as Caffeine does not know when the process has finished.
Any help would be appreciated,

Good thread on this issues at MacRumours (http://forums.macrumors.com/showthread.php?t=1415661). Suggested solution is to install Caffeine from the App Store (http://itunes.apple.com/us/app/caffe...11246225?mt=12).

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Imac sleeps whith hard disk activity

I have music playing on my hard drive using a Logitech Squeezebox but for some reason my Intel Imac using the latest software doesnt
recognize this and falls asleep at the time my imac is supposed to sleep at around 15 minutes.I have multiple Squeezeboxes and they all
will fall asleep when playing music on my Imac
This happened about 4 years ago but since then I havent had this issue so I assume its software related.
Any suggestion other then Pram reset. Ive done all that,restarted computer,etc.

RedDwarfUK wrote:
I havent really installed much as well. Here are the list of programs I have installed.
Adium
Firefox
New icons
app cleaner
skype
spotify
chicken of the VNC
GoToMeeting
Cisco VPN Client
Xmarks for safari and firefox
I would start by checking each of these items, making sure you have the latest versions of each & that they are compatible with Snow Leopard. Do the same for any Firefox extensions or any plugins associated with any of these applications. In particular, chicken of the VNC hasn't been updated since 2006 & what little compatibility info I can find for it suggests it supports only Tiger (10.4) & 10.3.9. The Download Xmarks page indicates that it is beta software.
Also note that some of these items may do more than just run as applications. On first run or install, some might install startup or login items, or preference panels that remain in effect even when the application is not running. Check /Library/StartupItems & /System/Library/StartupItems -- both are empty by default, so anything you find in them is suspect. Likewise, check the System Preferences > Accounts > Login Items tab. Anything you find in them that does not appear to come from Apple (like iTunes helper) is suspect. Also check the "Other" category of System Preferences.

IMac sleeps even when processing

Hi,
I have a very large DVD library which I have been (very) slowly converting so that I can watch them on my Apple TV. I don't want to get into arguments about whether or not you should rip DVDs etc, but I've been using Ripit and Handbrake to do so. After ripping the DVDs to the computer I use Handbrake to convert them. If I leave the computer processing these video files and walk away, the computer will go to sleep and stop processing. I always thought that if the computer is "working" then it shouldn't sleep? So surely it should only do so AFTER it's finshed converting the files. When I come back to it later and wake it, the conversion is paused. I could always click "never sleep" when converting, and have started doing that. But this seem wrong. Anyone have any ideas?
Thanks

Good thread on this issues at MacRumours (http://forums.macrumors.com/showthread.php?t=1415661). Suggested solution is to install Caffeine from the App Store (http://itunes.apple.com/us/app/caffe...11246225?mt=12).

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Macbook air runs hot and makes noise like processor running hard when connected to display - even when not actively using air book

macbook air runs hot and makes noise like processor running hard when connected to display - even when not actively using air book

You could use the free tool iStat Pro to see what changes when you connect your MBA to the display. Without doing anything the CPU pane should show a high percentage for "Idle". If the idle value is too low, launch the Activity Monitor and sort by CPU usage. There is a pane showing the different temperatures of your computer. Watch them for a few minutes after connecting the display.

Computer unresponsive with disk activity, even when disk is USB

Hi,
I've always had issues with responsiveness with Linux when there is disk activity (several distro's, same hardware), whereas a Windows XP installation reacts very snappily. When I have a torrent client open, Mplayer keeps hanging a few times a minute (even more often when the download is going fast (2 MB/s)).
Recently I migrated to ext4 in the hopes that would fix it, but it didn't. It's also not something as simple as a DMA issue (because it's SATA). Disk throughput is about 80 MB/s, which is OK.
Anyway, currently, I'm performing this on a USB disk:
dd if=/dev/zero of=/dev/sdc1 bs=10M
And even then the computer is almost unusable, which it shouldn't be, because the internal disks are not used for this. And some time back when I was copying an AVI to a USB stick, it was utterly unusable.
Maybe it's a driver issue, because I can't imagine the normal schedulers being so horrible, but I can't say.
My disk controller can't be accessed with AHCI (there is no 'native' option in the BIOS), yet NCQ is enabled:
# dmesg|grep -i ncq
[ 1.313605] ata3.00: 2930275055 sectors, multi 16: LBA48 NCQ (depth 0/32)
[ 1.800338] ata4.00: 2930277168 sectors, multi 16: LBA48 NCQ (depth 0/32)
[ 2.324738] ata6.00: 488395055 sectors, multi 16: LBA48 NCQ (depth 0/32)
I have kernel 3.1.1-1-ARCH, so I should have the 'wonder patch'.
Hardware:
CPU: Athlon X2 3800+ (2GHz dual core).
RAM: 2 GB DDR400 RAM.
Chipset: Nvidia nForce 4 ultra.
Disks (in MD RAID1): 2 WDC WD15EARS-00Z5B1 (disks have changed over the years) and 1 Seagate disk (which contains windows and is spun down in Linux, to prevent noise).
I disabled the (self-destructing) head parking feature of the caviar green disks with WDidle by setting the timeout to max (disabling the head parking with WDidle actually lets it trigger constantly, that's why I chose this way).
Lspci:
00:00.0 Memory controller: nVidia Corporation CK804 Memory Controller (rev a3)
00:01.0 ISA bridge: nVidia Corporation CK804 ISA Bridge (rev a3)
00:01.1 SMBus: nVidia Corporation CK804 SMBus (rev a2)
00:02.0 USB controller: nVidia Corporation CK804 USB Controller (rev a2)
00:02.1 USB controller: nVidia Corporation CK804 USB Controller (rev a3)
00:06.0 IDE interface: nVidia Corporation CK804 IDE (rev f2)
00:07.0 IDE interface: nVidia Corporation CK804 Serial ATA Controller (rev f3)
00:08.0 IDE interface: nVidia Corporation CK804 Serial ATA Controller (rev f3)
00:09.0 PCI bridge: nVidia Corporation CK804 PCI Bridge (rev a2)
00:0a.0 Bridge: nVidia Corporation CK804 Ethernet Controller (rev a3)
00:0b.0 PCI bridge: nVidia Corporation CK804 PCIE Bridge (rev a3)
00:0c.0 PCI bridge: nVidia Corporation CK804 PCIE Bridge (rev a3)
00:0d.0 PCI bridge: nVidia Corporation CK804 PCIE Bridge (rev a3)
00:0e.0 PCI bridge: nVidia Corporation CK804 PCIE Bridge (rev a3)
00:18.0 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] HyperTransport Technology Configuration
00:18.1 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] Address Map
00:18.2 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] DRAM Controller
00:18.3 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] Miscellaneous Control
01:07.0 Multimedia audio controller: Creative Labs SB Audigy (rev 04)
01:07.1 Input device controller: Creative Labs SB Audigy Game Port (rev 04)
01:07.2 FireWire (IEEE 1394): Creative Labs SB Audigy FireWire Port (rev 04)
01:08.0 Multimedia video controller: Brooktree Corporation Bt878 Video Capture (rev 11)
01:08.1 Multimedia controller: Brooktree Corporation Bt878 Audio Capture (rev 11)
05:00.0 VGA compatible controller: nVidia Corporation G96 [GeForce 9500 GT] (rev a1)
# cat /proc/mdstat ( which shows no write intent bitmap to slow it down):
Personalities : [raid1]
md1 : active raid1 sda2[0] sdb2[1]
1464969720 blocks super 1.0 [2/2] [UU]
md0 : active raid1 sda1[0] sdb1[1]
156788 blocks super 1.0 [2/2] [UU]
unused devices: <none>
Anybody know what might be causing this?

I recently tried to play around with the schedulers and I found out that using "deadline" for my internal drives, "cfq" for my optical drive and "noop" for everything else. I tried copying a load of small files on my USB flashdrive while playing a movie from the optical drive and the system felt very responsive.
I've been playing some more, and you're right in that it seems that with the internal disks at deadline, the system is a lot more responsive. Previously, I put the external disk I was zeroing at deadline too, but that (I know now) made it worse again.
I run a 3.2-rc5 kernel which seems to help considerably though.
Has there been any specific change in that kernel to cause that?
BTW, I noticed that the NCQ queue on your drives is of 0 length, try setting it o 31 like this (as root).
I always wondered about the NCQ queue. In pages about NCQ that I found, the dmesg also reported a queue of 0. I just always figured it meant how many commands it currently had, being zero at boot time.
When I do "cat /sys/block/sda/device/queue_depth" it always says one, regardless of disk activity.

Scheduled Backups even when no activity?

I leave my computer on all day while I'm at work and no one is using it. I noticed that Time Machine still makes hourly backups even though the computer doesn't have any activity occurring on it. Should this be happening? I would think this is a waste of resources during the day when there isnt really anything to back up. Shouldnt it only backing up hourly when there is activity on it?

that doesnt make any sense. If the computer is asleep, Tim Machine cant recognize that and know that there has been no disk activity? It would seem to me that nothing is changing if the computer is asleep. And therefore there is no reason for time machine to be running and backing up. The only time there is disk activity is when time machine wakes the computer to back itself up.

Is it normal to see my iPod in Explorer even when disk space is turned off?

For a while, I was using disk space to store stuff. After buying an external and trying to move files over to it, several files were somehow corrupted, causing several problems with Windows wanting to reformat my iPod. I ended up resetting the iPod to fix that... but now I can see my iPod in Windows Explorer, even though disk space is turned off. Is that normal?

rockmyplimsoul wrote:
darkpontiac wrote:
When its off, it will allow you to use your iPod while still plugged in provided its done syncing and it shouldn't disappear from iTunes unless disconnected.
This part has bugged me since somewhere around iTunes v7.1 ... it used to be that with disk mode disabled you could auto-sync your iPod, leave it connected to iTunes, make changes to your library (e.g. new playlists, update tags) and then re-sync the iPod (right-click/re-sync). Now, once the iPod completes the auto-sync it disconnects from iTunes (but stays in the source column) and in order to re-sync the iPod after making library changes, you have to physically disconnect and re-connect it. It didn't used to be this way ...
Actually the way it always worked for me with my older ipod I had was if i clicked sync while it was disconnected by still showing up in itunes, it would connect back and sync again and then when done go back to where its in the source list but disconnected.

Premiere Pro CS6 does not recognize USB PnP Sound device connected to iMac OSX even when activated in Audio MIDI setup. The iMac(i-7 processor,16 GB) is working with this USB device without any problem

Premiere Pro CS6 does not recognize the USB PnP Sound device in order to produce a commentary sound track. The USB device has been activated on the iMac OSX by using the Audio-MIDI-setup and is working correctly with the iMac. When opening > presets >audio hardware I can only select between >standard >out integrated > digital input integrated >microphone integrated. USB PnP is not indicated at this place.
With the built-in microphone of the iMac I can produce the commentary sound track, but I would prefer a stand alone version for better quality.
Your help is highly appreciated. Thanks in advance, Annemarie!

I'm using a Logitech Webcam Pro 9000 (which has a microphone on the side). I have several other devices plugged into separate USB slots: a keyboard, a mouse, my iPhone, and a Roland keyboard midi controller.
I've considered that maybe the webcam/mic combo is the culprit. If USB doesn't work at a constant speed, that could very well be causing the issue! The sound begins to lag badly sometimes when it's working properly, so that there's a multisecond delay between speaking and hearing my voice repeated back over the mic which is another sign that something is wrong. I've also caught it making a strange electronic sound during its "hang" time once it stops taking sound input correctly.
Maybe I should try to use line-in and forgo USB altogether then. I think I'd need a preamp and some sort of converter for that since the Mac Mini lacks a powered mic jack. I'm only a newbie musician so I've never set up such a system but it might be a better solution in the long run.
I'll check to see if it hangs before or after my computer enters suspend mode, that's a good suggestion too. Thank you for your help!

My imac goes to sleep even when in use

i ran the hardware test and got this message:logic board-error code 2 STH/1/2 CPU T-Diode
what should i do/

This is not only a logic board problem.
I had the same exact problems as you and have even got the same exact message. I ended up having to get the whole motherboard replaced because of one very simple but troubling problem.
The motherboard is designed as such where Apple put the the temperature sensor running from the hard drive right next to the CPU processor. Over time, the high heat of the CPU processor causes the plastic/rubber surrounding the wire to become brittle and even melt. When this happens, the system gets a bad reading from the hard drive and thusly causes a louder, faster fan noise; and eventually, the computer starts to fall asleep even while in use.
Simply put, you will probably need to have your mother board replaced. Contact Apple with your error code, and explain the problem carefully to them because it is not in the usual problems they have faced. I had my motherboard replaced at the end of April and it seems to be running fine for now.

My PowerBook G4 15-inch could turn to sleep even when I am using it.

It happened on Os X 10.3 since around 3 months ago and I have been suffering by it. sometimes, when I am typing something, suddenly the screen becomes black- it starts sleeping! and it will never wake up no matter how would I do. I have to remove the battery and wait until it died then I put battery back and restart it, I don't even have chance to save my work. I sent my PowerBook to apple care centre and they told me this is an operation system problem so I formated the hard disk and installed Os X 10.4, but the problem is still there. Can anyone give me suggestion? Is it a software problem or hardware problem? Thank you very much.

Hello Chen, Welcome to the Discussions!
Try resetting the PMU for your particular model, according to:
http://docs.info.apple.com/article.html?artnum=14449
If done correctly, you should need to reset your clock.
Does your pB seem abnormally warm?
Joe

Pdflush hanging disks when disk activity is high

Hi everyone! my "problem" is that when im copying or moving larga amounts of data between my partitions/disks my the system response is right, but the apps who show or access those disks hangs for a few seconds including the copy/moving itself, theres a lot of pdflush process that's what conky and htop show me when those little hangs appear... dont know if it has something to do, but the disk is a sata drive inside a usb case formatted as ext3... copying from that disk from the same disk or any other inside mi box (1 80gb IDE drive) cause those pdflush process to appear...
1. is this normal?
2. what is pdflush?
3. what it do exactly?
thanks!!!
EDIT: forgot to mention... cpu activity during those mini hangs is low... 5%-10% or less cpu usage... in a athlon xp 2600+ cpu... and pdflush processes are 0% using cpu... there are 5 or more of those pdflush...
Last edited by leo2501 (2007-08-27 10:44:24)

Auto SOLVED for anybody interested...
http://www.westnet.com/~gsmith/content/ … dflush.htm
The Linux Page Cache and pdflush:
Theory of Operation and Tuning for Write-Heavy Loads
As you write out data ultimately intended for disk, Linux caches this information in an area of memory called the page cache. You can find out basic info about the page cache using tools like free, vmstat or top. See http://gentoo-wiki.com/FAQ_Linux_Memory_Management to learn how to interpret top's memory information, or atop to get an improved version.
Full information about the page cache only shows up by looking at /proc/meminfo. Here is a sample from a system with 4GB of RAM:
MemTotal: 3950112 kB
MemFree: 622560 kB
Buffers: 78048 kB
Cached: 2901484 kB
SwapCached: 0 kB
Active: 3108012 kB
Inactive: 55296 kB
HighTotal: 0 kB
HighFree: 0 kB
LowTotal: 3950112 kB
LowFree: 622560 kB
SwapTotal: 4198272 kB
SwapFree: 4198244 kB
Dirty: 416 kB
Writeback: 0 kB
Mapped: 999852 kB
Slab: 57104 kB
Committed_AS: 3340368 kB
PageTables: 6672 kB
VmallocTotal: 536870911 kB
VmallocUsed: 35300 kB
VmallocChunk: 536835611 kB
HugePages_Total: 0
HugePages_Free: 0
Hugepagesize: 2048 kB
The size of the page cache itself is the "Cached" figure here, in this example it's 2.9GB. As pages are written, the size of the "Dirty" section will increase. Once writes to disk have begun, you'll see the "Writeback" figure go up until the write is finished. It can be very hard to actually catch the Writeback value going high, as its value is very transient and only increases during the brief period when I/O is queued but not yet written.
Linux usually writes data out of the page cache using a process called pdflush. At any moment, between 2 and 8 pdflush threads are running on the system. You can monitor how many are active by looking at /proc/sys/vm/nr_pdflush_threads. Whenever all existing pdflush threads are busy for at least one second, an additional pdflush daemon is spawned. The new ones try to write back data to device queues that are not congested, aiming to have each device that's active get its own thread flushing data to that device. Each time a second has passed without any pdflush activity, one of the threads is removed. There are tunables for adjusting the minimum and maximum number of pdflush processes, but it's very rare they need to be adjusted.
pdflush tunables
Exactly what each pdflush thread does is controlled by a series of parameters in /proc/sys/vm:
/proc/sys/vm/dirty_writeback_centisecs (default 500): In hundredths of a second, this is how often pdflush wakes up to write data to disk. The default wakes up the two (or more) active threads twice a second.
There can be undocumented behavior that thwarts attempts to decrease dirty_writeback_centisecs in an attempt to make pdflush more aggressive. For example, in early 2.6 kernels, the Linux mm/page-writeback.c code includes logic that's described as "if a writeback event takes longer than a dirty_writeback_centisecs interval, then leave a one-second gap". In general, this "congestion" logic in the kernel is documented only by the kernel source itself, and how it operates can vary considerably depending on which kernel you are running. Because of all this, it's unlikely you'll gain much benefit from lowering the writeback time; the thread spawning code assures that they will automatically run themselves as often as is practical to try and meet the other requirements.
The first thing pdflush works on is writing pages that have been dirty for longer than it deems acceptable. This is controlled by:
/proc/sys/vm/dirty_expire_centiseconds (default 3000): In hundredths of a second, how long data can be in the page cache before it's considered expired and must be written at the next opportunity. Note that this default is very long: a full 30 seconds. That means that under normal circumstances, unless you write enough to trigger the other pdflush method, Linux won't actually commit anything you write until 30 seconds later.
The second thing pdflush will work on is writing pages if memory is low. This is controlled by:
/proc/sys/vm/dirty_background_ratio (default 10): Maximum percentage of active that can be filled with dirty pages before pdflush begins to write them
Note that some kernel versions may internally put a lower bound on this value at 5%.
Most of the documentation you'll find about this parameter suggests it's in terms of total memory, but a look at the source code shows this isn't true. In terms of the meminfo output, the code actually looks at
MemFree + Cached - Mapped
So on the system above, where this figure gives 2.5GB, with the default of 10% the system actually begins writing when the total for Dirty pages is slightly less than 250MB--not the 400MB you'd expect based on the total memory figure.
Summary: when does pdflush write?
In the default configuration, then, data written to disk will sit in memory until either a) they're more than 30 seconds old, or b) the dirty pages have consumed more than 10% of the active, working memory. If you are writing heavily, once you reach the dirty_background_ratio driven figure worth of dirty memory, you may find that all your writes are driven by that limit. It's fairly easy to get in a situation where pages are always being written out by that mechanism well before they are considered expired by the dirty_expire_centiseconds mechanism.
Other than laptop_mode, which changes several parameters to optimize for keeping the hard drive spinning as infrequently as possible (see http://www.samwel.tk/laptop_mode/ for more information) those are all the important kernel tunables that control the pdflush threads.
Process page writes
There is another parameter involved though that can spill over into management of user processes:
/proc/sys/vm/dirty_ratio (default 40): Maximum percentage of total memory that can be filled with dirty pages before processes are forced to write dirty buffers themselves during their time slice instead of being allowed to do more writes.
Note that all processes are blocked for writes when this happens, not just the one that filled the write buffers. This can cause what is perceived as an unfair behavior where one "write-hog" process can block all I/O on the system. The classic way to trigger this behavior is to execute a script that does "dd if=/dev/zero of=hog" and watch what happens. See Kernel Korner: I/O Schedulers for examples showing this behavior.
Tuning Recommendations for write-heavy operations
The usual issue that people who are writing heavily encouter is that Linux buffers too much information at once, in its attempt to improve efficiency. This is particularly troublesome for operations that require synchronizing the filesystem using system calls like fsync. If there is a lot of data in the buffer cace when this call is made, the system can freeze for quite some time to process the sync.
Another common issue is that because so much must be written before any phyiscal writes start, the I/O appears more bursty than would seem optimal. You'll have long periods where no physical writes happen at all, as the large page cache is filled, followed by writes at the highest speed the device can achieve once one of the pdflush triggers is tripped.
dirty_background_ratio: Primary tunable to adjust, probably downward. If your goal is to reduce the amount of data Linux keeps cached in memory, so that it writes it more consistently to the disk rather than in a batch, lowering dirty_background_ratio is the most effective way to do that. It is more likely the default is too large in situations where the system has large amounts of memory and/or slow physical I/O.
dirty_ratio: Secondary tunable to adjust only for some workloads. Applications that can cope with their writes being blocked altogether might benefit from substantially lowering this value. See "Warnings" below before adjusting.
dirty_expire_centisecs: Test lowering, but not to extremely low levels. Attempting to speed how long pages sit dirty in memory can be accomplished here, but this will considerably slow average I/O speed because of how much less efficient this is. This is particularly true on systems with slow physical I/O to disk. Because of the way the dirty page writing mechanism works, trying to lower this value to be very quick (less than a few seconds) is unlikely to work well. Constantly trying to write dirty pages out will just trigger the I/O congestion code more frequently.
dirty_writeback_centisecs: Leave alone. The timing of pdflush threads set by this parameter is so complicated by rules in the kernel code for things like write congestion that adjusting this tunable is unlikely to cause any real effect. It's generally advisable to keep it at the default so that this internal timing tuning matches the frequency at which pdflush runs.
Swapping
By default, Linux will aggressively swap processes out of physical memory onto disk in order to keep the disk cache as large as possible. This means that pages that haven't been used recently will be pushed into swap long before the system even comes close to running out of memory, which is an unexpected behavior compared to some operating systems. The /proc/sys/vm/swappiness parameter controls how aggressive Linux is in this area.
As good a description as you'll find of the numeric details of this setting is in section 4.15 of http://people.redhat.com/nhorman/papers/rhel4_vm.pdf It's based on a combination of how much of memory is mapped (that total is in /proc/meminfo) as well as how difficult it has been for the virtual memory manager to find pages to use.
A value of 0 will avoid ever swapping out just for caching space. Using 100 will always favor making the disk cache bigger. Most distributions set this value to be 60, tuned toward moderately aggressive swapping to increase disk cache.
The optimal setting here is very dependant on workload. In general, high values maximize throughput: how much work your system gets down during a unit of time. Low values favor latency: getting a quick response time from applications. Some desktop users so favor low latency that they set swappiness to 0, so that user applications are never swapped to disk (as can happen when the system is executing background tasks while the user is away). That's perfectly reasonable if the amount of memory in the system exceeds the usual working set for the applications used. Servers that are very active and usually throughput bound could justify setting it to 100. On the flip side, a desktop system that is so limited in memory that every active byte helps might also prefer a setting of 100.
Since the size of the disk cache directly determines things like how much dirty data Linux will allow in memory, adjusting swappiness can greatly influence that behavior even though it's not directly tied to that.
Warnings
-There is a currently outstanding Linux kernel bug that is rare and difficult to trigger even intentionally on most kernel versions. However, it is easier to encounter when reducing dirty_ratio setting below its default. An introduction to the issue starts at http://lkml.org/lkml/2006/12/28/171 and comments about it not being specific to the current kernel release are at http://lkml.org/lkml/2006/12/28/131
-The standard Linux memory allocation behavior uses an "overcommit" setting that allows processes to allocate more memory than is actually available were they to all ask for their pages at once. This is aimed at increasing the amount of memory available for the page cache, but can be dangerous for some types of applications. See http://www.linuxinsight.com/proc_sys_vm … emory.html for a note on the settings you can adjust. An example of an application that can have issues when overcommit is turned on is PostgreSQL; see "Linux Memory Overcommit" at http://www.postgresql.org/docs/current/ … urces.html for their warnings on this subject.
References: page cache
Neil Horman, "Understanding Virtual Memory in Red Hat Enterprise Linux 4" http://people.redhat.com/nhorman/papers/rhel4_vm.pdf
Daniel P. Bovet and Marco Cesati, "Understanding the Linux Kernel, 3rd edition", chapter 15 "The Page Cache". Available on the web at http://www.linux-security.cn/ebooks/ulk3-html/
Robert Love, "Linux Kernel Development, 2nd edition", chapter 15 "The Page Cache and Page Writeback"
"Runtime Memory Management", http://tree.celinuxforum.org/CelfPubWik … easurement
"Red Hat Enterprise Linux-Specific [Memory] Information", http://www.redhat.com/docs/manuals/ente … lspec.html
"Tuning Swapiness", http://kerneltrap.org/node/3000
"FAQ Linux Memory Management", http://gentoo-wiki.com/FAQ_Linux_Memory_Management
From the Linux kernel tree:
* Documentation/filesystems/proc.txt (the meminfo documentation there originally from http://lwn.net/Articles/28345/)
* Documentation/sysctl/vm.txt
* Mm/page-writeback.c
References: I/O scheduling
While not directly addressed here, the I/O scheduling algorithms in Linux actually handle the writes themselves, and some knowledge or tuning of them may be synergistic with adjusting the parameters here. Adjusting the scheduler only makes sense in the context where you've already configured the page cache flushing correctly for your workload.
D. John Shakshober, "Choosing an I/O Scheduler for Red Hat Enterprise Linux 4 and the 2.6 Kernel" http://www.redhat.com/magazine/008jun05 … chedulers/
Robert Love, "Kernel Korner: I/O Schedulers", http://www.linuxjournal.com/article/6931
Seelam, Romero, and Teller, "Enhancements to Linux I/O Scheduling", http://linux.inet.hr/files/ols2005/seelam-reprint.pdf
Heger, D., Pratt, S., "Workload Dependent Performance Evaluation of the Linux 2.6 I/O Schedulers", http://linux.inet.hr/files/ols2004/pratt-reprint.pdf
Upcoming Linux work in progress
-There is a patch in testing from SuSE that adds a parameter called dirty_ratio_centisecs to the kernel tuning which fine-tunes the write-throttling behavior. See "Patch: per-task predictive write throttling" at http://lwn.net/Articles/152277/ and Andrea Arcangeli's article (which has a useful commentary on the existing write throttling code) at http://www.lugroma.org/contenuti/eventi … rnel26.pdf
-SuSE also has suggested a patch at http://lwn.net/Articles/216853/ that allows setting the dirty_ratio settings below the current useful range, aimed at systems with very large memory capacity. The commentary on this patch also has some helpful comments on improving dirty buffer writing, although it is fairly specific to ext3 filesystems.
-The stock 2.6.22 Linux kernel has substantially reduced the default values for the dirty memory parameters. dirty_background_ratio defaulted to 10, now it defaults to 5. vm_dirty_ratio defaulted to 40, now it's 10
-A recent lively discussion on the Linux kernel mailing list discusses some of the limitations of the fsync mechanism when using ext3.
Copyright 2007 Gregory Smith. Last update 8/08/2007.

IPod Showing Up As Removable Disk Even When Disk Use is Disabled

Hi there,
I'm having a problem with my iPod and Vista. My iPod is showing up as a removable disk even though I do not have "Enable Disk Use" checked. This is confirmed by the fact that I can disconnect my iPod without having to eject it first.
I've tried checking and unchecking the text box. It works the first time, but when I reconnect the iPod, the disk shows up again.
How can I permanently disable disk use?
Appreciate any help you can give.

Have you tried performing a RESTORE on the iPod when connected to iTunes?
Patrick

How can you remove old conversations from the iMac. Even when I remove them they return when I start a new conversation with the same person. Only happens on iMac with the Beta iMessage program

How do you remove an old conversation using the Beta iMessage on an iMac. When I open a new conversation with the same person the old conversation comes back

Hi,
Previously iChat had tried a Last Chat/IM option when using Saved Transcripts - which itself was an option.
iChat has also tried "Saving" the Last Chat by leaving a Chat window open and using something similar to the Lion method of showing an app in the state is was closed in.
In Messages the option to Save Transcripts has been removed and Chats or all types are saved as a matter of course.
What this tends to mean for your iChat style Buddy Chats is that it opens all the Transcripts for that buddy as a sort of History you can scroll back through if you want (I have some Buddies with saved chats gong back to 2004)
With the Syncing of iMessages with iPhones and iPads (or Touches) then it seems this works slightly differently.
Although you can delete the chat and the contents of the Chat as separate action it is true that in the Beta as soon as you connect to the same Contact that the contents of the previous chats are shown to you.
I have found that Messages stores a data base of info on iMessages in Your Home Folder/Library/Messages
I have found that deleting this chat-db removes the "History" that keep popping up.
By default the Saved "iChats" are also stored in the Home Folder/Documents/iChats (At least this is the default place iChat used and they go to the same iChats folder where ever you had it)
Some people claim removing iMessages saved here stops the "History" reappearing.
In Lion the only access to the Home Folder/Library is via the Finder's Go Menu and hiding down the ALT key
10:00 PM Sunday; June 10, 2012
Please, if posting Logs, do not post any Log info after the line "Binary Images for iChat"
 iMac 2.5Ghz 5i 2011 (Lion 10.7.4)
 G4/1GhzDual MDD (Leopard 10.5.8)
 MacBookPro 2Gb (Snow Leopard 10.6.8)
 Mac OS X (10.7.4),
"Limit the Logs to the Bits above Binary Images."  No, Seriously

Screen goes to sleep even when viewing movies in full screen mode

Hi, I have adjusted my settings so my screen goes to sleep after 5 minutes which is ok. But it also does this when viewing movies in full screen mode.... Is this a setting somewhere? Thanx!

Welcome to the Discussions!
"When the computer is inactive" or "idle" means when YOU, the user, are doing nothing, neither using the keyboard nor the mouse. So you have to increase that 5 mins in Energy Saver.
Andreas

IMac sleeps even when disk activity is occurring - Mavericks

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