On Thu, 17 Mar 2016, Robert LeBlanc wrote: > We are trying to figure out how to use rados bench to reproduce. Ceph > itself doesn't seem to think there is any corruption, but when you do a > verify inside the RBD, there is. Can rados bench verify the objects after > they are written? It also seems to be primarily the filesystem metadata > that is corrupted. If we fsck the volume, there is missing data (put into > lost+found), but if it is there it is primarily OK. There only seems to be > a few cases where a file's contents are corrupted. I would suspect on an > object boundary. We would have to look at blockinfo to map that out and see > if that is what is happening. 'rados bench' doesn't do validation. ceph_test_rados does, though--if you can reproduce with that workload then it should be pretty easy to track down. Thanks! sage > We stopped all the IO and did put the tier in writeback mode with recency > 1, set the recency to 2 and started the test and there was corruption, so > it doesn't seem to be limited to changing the mode. I don't know how that > patch could cause the issue either. Unless there is a bug that reads from > the back tier, but writes to cache tier, then the object gets promoted > wiping that last write, but then it seems like it should not be as much > corruption since the metadata should be in the cache pretty quick. We > usually evited the cache before each try so we should not be evicting on > writeback. > > Sent from a mobile device, please excuse any typos. > On Mar 17, 2016 6:26 AM, "Sage Weil" <sweil@xxxxxxxxxx> wrote: > > > On Thu, 17 Mar 2016, Nick Fisk wrote: > > > There is got to be something else going on here. All that PR does is to > > > potentially delay the promotion to hit_set_period*recency instead of > > > just doing it on the 2nd read regardless, it's got to be uncovering > > > another bug. > > > > > > Do you see the same problem if the cache is in writeback mode before you > > > start the unpacking. Ie is it the switching mid operation which causes > > > the problem? If it only happens mid operation, does it still occur if > > > you pause IO when you make the switch? > > > > > > Do you also see this if you perform on a RBD mount, to rule out any > > > librbd/qemu weirdness? > > > > > > Do you know if it’s the actual data that is getting corrupted or if it's > > > the FS metadata? I'm only wondering as unpacking should really only be > > > writing to each object a couple of times, whereas FS metadata could > > > potentially be being updated+read back lots of times for the same group > > > of objects and ordering is very important. > > > > > > Thinking through it logically the only difference is that with recency=1 > > > the object will be copied up to the cache tier, where recency=6 it will > > > be proxy read for a long time. If I had to guess I would say the issue > > > would lie somewhere in the proxy read + writeback<->forward logic. > > > > That seems reasonable. Was switching from writeback -> forward always > > part of the sequence that resulted in corruption? Not that there is a > > known ordering issue when switching to forward mode. I wouldn't really > > expect it to bite real users but it's possible.. > > > > http://tracker.ceph.com/issues/12814 > > > > I've opened a ticket to track this: > > > > http://tracker.ceph.com/issues/15171 > > > > What would be *really* great is if you could reproduce this with a > > ceph_test_rados workload (from ceph-tests). I.e., get ceph_test_rados > > running, and then find the sequence of operations that are sufficient to > > trigger a failure. > > > > sage > > > > > > > > > > > > > > > > > > > -----Original Message----- > > > > From: ceph-users [mailto:ceph-users-bounces@xxxxxxxxxxxxxx] On Behalf > > Of > > > > Mike Lovell > > > > Sent: 16 March 2016 23:23 > > > > To: ceph-users <ceph-users@xxxxxxxxxxxxxx>; sweil@xxxxxxxxxx > > > > Cc: Robert LeBlanc <robert.leblanc@xxxxxxxxxxxxx>; William Perkins > > > > <william.perkins@xxxxxxxxxxxxx> > > > > Subject: Re: data corruption with hammer > > > > > > > > just got done with a test against a build of 0.94.6 minus the two > > commits that > > > > were backported in PR 7207. everything worked as it should with the > > cache- > > > > mode set to writeback and the min_read_recency_for_promote set to 2. > > > > assuming it works properly on master, there must be a commit that we're > > > > missing on the backport to support this properly. > > > > > > > > sage, > > > > i'm adding you to the recipients on this so hopefully you see it. the > > tl;dr > > > > version is that the backport of the cache recency fix to hammer > > doesn't work > > > > right and potentially corrupts data when > > > > the min_read_recency_for_promote is set to greater than 1. > > > > > > > > mike > > > > > > > > On Wed, Mar 16, 2016 at 4:41 PM, Mike Lovell > > > > <mike.lovell@xxxxxxxxxxxxx> wrote: > > > > robert and i have done some further investigation the past couple days > > on > > > > this. we have a test environment with a hard drive tier and an ssd > > tier as a > > > > cache. several vms were created with volumes from the ceph cluster. i > > did a > > > > test in each guest where i un-tarred the linux kernel source multiple > > times > > > > and then did a md5sum check against all of the files in the resulting > > source > > > > tree. i started off with the monitors and osds running 0.94.5 and > > never saw > > > > any problems. > > > > > > > > a single node was then upgraded to 0.94.6 which has osds in both the > > ssd and > > > > hard drive tier. i then proceeded to run the same test and, while the > > untar > > > > and md5sum operations were running, i changed the ssd tier cache-mode > > > > from forward to writeback. almost immediately the vms started > > reporting io > > > > errors and odd data corruption. the remainder of the cluster was > > updated to > > > > 0.94.6, including the monitors, and the same thing happened. > > > > > > > > things were cleaned up and reset and then a test was run > > > > where min_read_recency_for_promote for the ssd cache pool was set to 1. > > > > we previously had it set to 6. there was never an error with the > > recency > > > > setting set to 1. i then tested with it set to 2 and it immediately > > caused > > > > failures. we are currently thinking that it is related to the backport > > of the fix > > > > for the recency promotion and are in progress of making a .6 build > > without > > > > that backport to see if we can cause corruption. is anyone using a > > version > > > > from after the original recency fix (PR 6702) with a cache tier in > > writeback > > > > mode? anyone have a similar problem? > > > > > > > > mike > > > > > > > > On Mon, Mar 14, 2016 at 8:51 PM, Mike Lovell > > > > <mike.lovell@xxxxxxxxxxxxx> wrote: > > > > something weird happened on one of the ceph clusters that i administer > > > > tonight which resulted in virtual machines using rbd volumes seeing > > > > corruption in multiple forms. > > > > > > > > when everything was fine earlier in the day, the cluster was a number > > of > > > > storage nodes spread across 3 different roots in the crush map. the > > first > > > > bunch of storage nodes have both hard drives and ssds in them with the > > hard > > > > drives in one root and the ssds in another. there is a pool for each > > and the > > > > pool for the ssds is a cache tier for the hard drives. the last set of > > storage > > > > nodes were in a separate root with their own pool that is being used > > for burn > > > > in testing. > > > > > > > > these nodes had run for a while with test traffic and we decided to > > move > > > > them to the main root and pools. the main cluster is running 0.94.5 > > and the > > > > new nodes got 0.94.6 due to them getting configured after that was > > > > released. i removed the test pool and did a ceph osd crush move to move > > > > the first node into the main cluster, the hard drives into the root > > for that tier > > > > of storage and the ssds into the root and pool for the cache tier. > > each set was > > > > done about 45 minutes apart and they ran for a couple hours while > > > > performing backfill without any issue other than high load on the > > cluster. > > > > > > > > we normally run the ssd tier in the forward cache-mode due to the ssds > > we > > > > have not being able to keep up with the io of writeback. this results > > in io on > > > > the hard drives slowing going up and performance of the cluster > > starting to > > > > suffer. about once a week, i change the cache-mode between writeback > > and > > > > forward for short periods of time to promote actively used data to the > > cache > > > > tier. this moves io load from the hard drive tier to the ssd tier and > > has been > > > > done multiple times without issue. i normally don't do this while > > there are > > > > backfills or recoveries happening on the cluster but decided to go > > ahead > > > > while backfill was happening due to the high load. > > > > > > > > i tried this procedure to change the ssd cache-tier between writeback > > and > > > > forward cache-mode and things seemed okay from the ceph cluster. about > > > > 10 minutes after the first attempt a changing the mode, vms using the > > ceph > > > > cluster for their storage started seeing corruption in multiple forms. > > the > > > > mode was flipped back and forth multiple times in that time frame and > > its > > > > unknown if the corruption was noticed with the first change or > > subsequent > > > > changes. the vms were having issues of filesystems having errors and > > getting > > > > remounted RO and mysql databases seeing corruption (both myisam and > > > > innodb). some of this was recoverable but on some filesystems there was > > > > corruption that lead to things like lots of data ending up in the > > lost+found and > > > > some of the databases were un-recoverable (backups are helping there). > > > > > > > > i'm not sure what would have happened to cause this corruption. the > > libvirt > > > > logs for the qemu processes for the vms did not provide any output of > > > > problems from the ceph client code. it doesn't look like any of the > > qemu > > > > processes had crashed. also, it has now been several hours since this > > > > happened with no additional corruption noticed by the vms. it doesn't > > > > appear that we had any corruption happen before i attempted the > > flipping of > > > > the ssd tier cache-mode. > > > > > > > > the only think i can think of that is different between this time > > doing this > > > > procedure vs previous attempts was that there was the one storage node > > > > running 0.94.6 where the remainder were running 0.94.5. is is possible > > that > > > > something changed between these two releases that would have caused > > > > problems with data consistency related to the cache tier? or > > otherwise? any > > > > other thoughts or suggestions? > > > > > > > > thanks in advance for any help you can provide. > > > > > > > > mike > > > > > > > > > > > > > > > > > > _______________________________________________ > > ceph-users mailing list > > ceph-users@xxxxxxxxxxxxxx > > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > > > > >
_______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
