On 12/13/2011 03:10 PM, Ray Morris wrote: > > On Tue, 13 Dec 2011 13:35:46 -0500 > "Peter M. Petrakis" <peter.petrakis@canonical.com> wrote: > > >> Do you by any chance have active LVM snapshots? If so how many and >> how long have they been provisioned for? > > I forgot to mention that. There are now three snapshots, one on each of What distro and kernel on you on? > three LVs, that have been provisioned for a few hours. These LVs aren't > in active use, but are backups, synced daily. So basically the only > activity is rsync once daily, bandwidth limited to be fairly slow. One > logical volume that locked up when trying to write to it had a snapshot. LVM snapshots can be very I/O intensive, even when you're not directly using them. > Prior to this most recent rebuild, there were a lot of snap shots - > three on each of fifteen LVs. I replaced that VG with a fresh one > and it seemed to work for a while. I thought the problem was likely > related to lots of long lived snapshots, but after completely rebuilding > the VG after deleting all snapshots the problem recurred very quickly, > before there were many snapshots and before there was a lot of IO > to the snaps > > I realize I'm somewhat abusing snapshots - they weren't designed to > be long lived. Therefore my "torture test" usage may reveal problems > that wouldn't happen often with very short lived snapshots. That's right :). Some have reported as high as 50% impact on performance. > Another similar server has more snapshots on more LVs running the > same rsyncs without obvious trouble. > > I should also have mentioned sequential writes to one LV at a time > don't seem to trigger the problem. I copied the whole VG one LV > at a time with: > dd if=/dev/oldvg/lv1 of=/dev/newvg/lv1 > Copying the entire LVs sequentially saw no problems. Later when I tried > to rsync to the LVs the problem showed itself. That's remarkable as it removes the fs from the equation. What fs are you using? > >>>> filter = [ "a|^/dev/md.*|", "a|^/dev/sd.*|", >>>> "a|^/dev/etherd/.*|","r|^/dev/ram.*|", "r|block|", "r/.*/" ] >>> >> Is it intentional to include sd devices? Just because the MD uses >> them doesn't mean you have to make allowances for them here. > > > Some /dev/sdX devices were used, but no more and I have now removed > sd.* and etherd. > > >>> < locking_dir = "/var/lock/lvm" >>> --- >>>> locking_dir = "/dev/shm" >> >> Why? > > This was changed AFTER the problem started. > Because comment in the file says: > > # Local non-LV directory that holds file-based locks while commands > # are in progress. > > Because /var/lock is on an LV, I tried switching it to a directory that > will never be on an LV. That didn't seem to have any effect. Not a bad idea. Returning to the backtrace: ... Dec 13 09:15:52 clonebox3 kernel: [<ffffffffa01feca5>] raid5_quiesce+0x125/0x1a0 [raid456] Dec 13 09:15:52 clonebox3 kernel: [<ffffffff8105c580>] ? default_wake_function+0x0/0x20 Dec 13 09:15:52 clonebox3 kernel: [<ffffffff810563f3>] ? __wake_up+0x53/0x70 Dec 13 09:15:52 clonebox3 kernel: [<ffffffffa02070c1>] make_request+0x501/0x520 [raid456] Dec 13 09:15:52 clonebox3 kernel: [<ffffffff8102ea69>] ? native_smp_send_reschedule+0x49/0x60 Dec 13 09:15:52 clonebox3 kernel: [<ffffffff810508e8>] ? resched_task+0x68/0x80 Dec 13 09:15:52 clonebox3 kernel: [<ffffffff813d09fb>] md_make_request+0xcb/0x230 Dec 13 09:15:52 clonebox3 kernel: [<ffffffff8105c484>] ? try_to_wake_up+0x284/0x380 Dec 13 09:15:52 clonebox3 kernel: [<ffffffff81241982>] generic_make_request+0x1b2/0x4f0 ... Dec 13 09:15:52 clonebox3 kernel: [<ffffffffa00029c4>] ? dm_wait_for_completion+0xd4/0x100 [dm_mod] Dec 13 09:15:52 clonebox3 kernel: [<ffffffffa0003836>] dm_flush+0x56/0x70 [dm_mod] Dec 13 09:15:52 clonebox3 kernel: [<ffffffffa00038a4>] dm_wq_work+0x54/0x200 [dm_mod] ... Dec 13 09:15:52 clonebox3 kernel: INFO: task kcopyd:31629 blocked for more than 120 seconds. Dec 13 09:15:52 clonebox3 kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. Dec 13 09:15:52 clonebox3 kernel: kcopyd D ffff88007b824700 0 31629 2 0x00000080 Dec 13 09:15:52 clonebox3 kernel: ffff880044aa7ac0 0000000000000046 ffff880044aa7a88 ffff880044aa7a84 Dec 13 09:15:52 clonebox3 kernel: ffff880044aa7ae0 ffff88007b824700 ffff880001e16980 00000001083f7280 raid5_quiesce should have been straight forward http://lxr.linux.no/linux+v3.1.5/drivers/md/raid5.c#L5422 >From the stack context I expect it to in case 2 or 0. It could also be stuck on a lock or it really did stop writes. At this point I think you might have more of an MD issue than anything else. If you could take MD out of the picture by using a single disk or use a HW RAID, that would be a really useful data point. I would also investigate the health of your RAID. Look back in the logs for members being ejected and then re-introduced. Also if you have any scripts that use mdadm to ping the array for status you might want to stop those too. Sounds like the linux-raid list is your next stop. Peter _______________________________________________ linux-lvm mailing list linux-lvm@redhat.com https://www.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
