On 09/12/2010 06:05 PM, Marcus D. Leech wrote: >> >> On 09/13/2010 12:12 AM, Marcus D. Leech wrote: >> >>> I have a new F12 system that is experiencing *agonizingly slow* SATA HDD >>> performance, and I >>> can't figure out why. No errors messages at all, just *really slow*. >>> >> Sounds like a bad disk to me. Run some diagnostic with smartctl (from >> the smartmontools package). What does 'smartctl -H /dev/sda' return ? >> (replace sda by your disk name if it's different). >> >> What's the content of the error log ? (smartctl -l error /dev/sda) A >> non-empty error log is a good sign the disk is on the down curve. >> >> Next, run a quick self test (smartctl -t short /dev/sda), wait 2 minutes >> then check the result with "smartctl -l selftest". >> >> If that succeeds, run a long test (smart -t long /dev/sda), which takes >> about 2 hours. >> > OK, I"ll check that out. > > In the mean-time, this is a WD Caviar GREEN drive, which I understand > has the intensely-brain-dead > "feature" that it'll unload the heads after 8 seconds of idle, which > may be part of the problem, since > I have *lots* of spare memory, and the kernel only flushes every 30 > seconds, which means that > it'll have to wait for the heads to re-load almost every time it flushes. > > There's supposed to be a DOS-based utility from WD to change the timers > (or turn them off). You almost certainly have a drive with a 4KB physical sector size, and it will suffer a 10-fold drop in write performance if your partitions do not start on logical (512-byte) sector numbers that are a multiple of 8. Align your partitions properly, and all is well. More and more drives are coming out with that 4KB physical sector size, so you're going to have to bite that bullet eventually. The issue with the 8-second idle timeout is drive wear out, not performance. The drives have a rating of 300,000 or 600,000 load/unload cycles. I never noticed any performance hit, and only realized there was a problem when smartctl showed the Load_Cycle_Count halfway to its maximum after just a couple of months. If your drives are unloading the heads twice a minute, those drives don't have long to live. Do the math. The DOS utility for changing/disabling that absurd idle timing can be found at: http://support.wdc.com/product/download.asp?groupid=609&sid=113&lang=en Ignore the dire warnings on that page. The program doesn't touch the firmware. It just sets one vendor-specific configuration parameter, and it works on many drive models, not just the odd ones listed. You do need to run it with only the W-D drive connected to the system. Whatever setting you choose (disabled, or a longer timeout) is persistent over power cycling. -- Bob Nichols "NOSPAM" is really part of my email address. Do NOT delete it. -- users mailing list users@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe or change subscription options: https://admin.fedoraproject.org/mailman/listinfo/users Guidelines: http://fedoraproject.org/wiki/Mailing_list_guidelines
