On Thu, Feb 28, 2008 at 3:38 AM, Tomasz Chmielewski <mangoo@xxxxxxxx> wrote: > Lately, I had a serious performance problem on a 1.2 TB ext3 filesystem > placed on LVM, which was placed on Linux RAID-5. > > Luckily, it was possible to alleviate much of this problem by removing > internal bitmap from RAID-5 and by using anticipatory IO scheduler. > > > As suggested earlier by Theodore Tso in "very poor ext3 write > performance on big filesystems" thread on linux-fsdevel list, I should > have used "mke2fs -E stride option to make sure all of the bitmaps > don't get concentrated on one hard drive spindle". > > > Although the fine mkfs.ext3 manual gives some basic information on how > to do it if you place the whole filesystem on a RAID array, it is not > clear to me how it should be done correctly if I want to create a ext3 > filesystem on LVM on RAID-5. > > Any helpful hints? I can't help with the stride stuff, as I use LVM and that makes the stride stuff utterly useless anyway. However, a suggestion I have for you which I found helped a great deal was to place the bitmap on some /other/ device's filesystem (I used a /etc/bitmaps/). Obviously, don't put it on a FS which is part of the raid, I typically divide each device into 2 or more raids, but only if I don't have enough devices for /system/ and /data/ -style pools. -- Jon -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
