On 25.03.2013, at 21:45, Mike Snitzer wrote: > On Fri, Mar 22 2013 at 11:12am -0400, > Andres Toomsalu <andres@active.ee> wrote: > >> Update! Issue seems to be active only with PERC H800 and MD1200 disks - local raid with PERC H700 and lvm thin lv-s work fine without corrupting on reboot. >> >> >> We stumbled on strange lvm thinly provisioned LV filesystem corruption case - here are steps that reproduce the issue: >> >> lvcreate --thinpool pool -L 8T --poolmetadatasize 16G VolGroupL1 >> lvcreate -T VolGroupL1/pool -V 2T --name thin_storage >> mkfs.ext4 /dev/VolGroupL1/thin_storage >> mount /dev/VolGroupL1/thin_storage /storage/ >> reboot > > Couple things: > 1) mkfs.ext4 does buffered IO so there is no gaurantee the superblock or > any other block group destriptors, have actually been committed to > non-volatile storage when mkfs.ext4 completes I see. While this could have been true during the tests I did later after discovering the issue - its a bit unlikely the case for first time the issue appeared - as there was about 24h time window between mkfs and host reboot then - and data was copied into new /storage LV. One more strange thing about the issue - during the tests I made repeatedly thin LV setups cycles with different pool, pool metadata and lv sizes - from 50G to 8TB - which seemed not to affect anything. Once it failed - it failed repeatedly - until the moment it started to work again and then it worked repeatedly - that behaviour actually could support the buffered IO theory… Right now I cant reproduce the issue anymore at will - waiting for failure again. > 2) reboot sequence is very distro specific; /storage may not have been > unmounted before reboot -- if it was unmounted then all data > should've been pushed out to non-volatile storage Distro is CentOS 6.4 - should unmount LV-s correctly as far as I know. > > So if you add this to command before "reboot" do you no longer have > missing data after the system reboots?: > > echo 3 > /proc/sys/vm/drop_caches will try next time > >> # NB! without host reboot unmount/mount succeeds! >> >> [root@node3 ~]# mount /dev/VolGroupL1/thin_storage /storage/ >> mount: you must specify the filesystem type >> >> Tried also to set poolmetadatasize to 2G, 14G, 15G and pool size to 1T, 2T - no change - corruption still happens. >> >> Hardware setup: >> * Underlaying block device (sdb) is hosted by PERC H800 controller and disks are coming from SAS disk expansion box (DELL MD1200). > ... >> What could be the issue here? > > I assume by "reboot" you mean the host (with the PERC card) never loses > power? Yes - soft reboot - no power cut. > > What layers of hardware writeback caching are in place in the > H800+MD1200 case vs H700+localraid? H800 has RAID10 array with cache set to 'writethrough' H700 has RAID10 array with cache set to 'writeback' _______________________________________________ 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/
