Re: Slow disks.
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On Sun, Dec 26, 2010 at 4:34 PM, Rogier Wolff <R.E.Wolff@xxxxxxxxxxxx> wrote: > On Sun, Dec 26, 2010 at 03:38:51PM -0800, Mark Knecht wrote: >> First, the drives are 4K sector so it's really important to get them >> on the right partition boundary. Installing Gentoo requires that we >> un-tar some large-ish files. IIRC on a 512 byte boundary these drives >> took 20-30 minutes to do this. On a 4K boundary they took about 1 >> minute. I know that doesn't make sense but those were my numbers, and >> it's a very high end Intel i7-980x MB so there wasn't any other >> problem I could find. > > Mark, > > Thanks for your contribution. You're seeing a 20-30 fold performance > issue, where only about 2x would be expected. So to test this theory > I'll see if we can evacuate a partition, untar a large-ish file as a > benchmark, and then see if we can improve that by changing the > alignment of the partition. (hmm. Maybe we should do things the other > way around. First find a tar-workload that takes about 1 minute on a > properly working drive, and then we can wait up to 30 minutes for it > to finish on the improper setup.). > > Being able to reproduce a problem at will is a great progress to being > able to solve it! > > Â Â Â ÂRoger. I hope my memory isn't way off on those numbers. I can certainly recall that the difference was remarkable and was very easy to demonstrate. 1) Partition the disk with fdisk placing a partition at sector 63, the typical first address we're given. Untar a Gentoo Stage 3 release snapshot such as http://gentoo.osuosl.org/releases/amd64/current-stage3/stage3-amd64-20101223.tar.bz2 2) Create a second partition starting at sector 1000 and do it again. It was day and night. If it was only the performance difference that would be one thing but the problem i had with these WD10EARS drives was sometimes they would just hang for long periods. In a RAID they just got kicked. The kernel was modern for the time I was building the machines, maybe 7-9 months ago. Hope this helps, Mark -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html