Hi Simon, Do you mean both standalone DB and(!!) standalone WAL devices/partitions by having SSD DB/WAL? If so then BlueFS might eventually overwrite some data at you DB volume with BlueFS log content. Which most probably makes OSD crash and unable to restart one day. This is quite random and not very frequent event which is to some degree dependent from cluster loading. And the period between actual data corruption and any evidence of this is non-zero most of the time - we tend to see it mostly when RocksDB was performing compaction. Other OSD configuration which might suffer from the issue is main device + WAL devices. Much less failure probability exists for main + DB layout. It requires almost full DB to get any chances to appear. Main-only device configurations aren't under the threat as far as I can tell. Thanks, Igor On 11/15/2019 12:40 PM, Simon Ironside wrote:
Hi,
I have two new-ish 14.2.4 clusters that began life on 14.2.0 , all with HDD OSDs with SSD DB/WALs but neither have experienced obvious problems yet.
What's the impact of this? Does possible data corruption mean possible silent data corruption? Or does the corruption cause the OSD failures mentioned on the tracker and you're basically ok if you either haven't had a failure or if you keep on top of failures the way you would if they were normal disk failures?
Thanks, Simon
On 14/11/2019 16:10, Sage Weil wrote:
Hi everyone,
We've identified a data corruption bug[1], first introduced[2] (by yours truly) in 14.2.3 and affecting both 14.2.3 and 14.2.4. The corruption appears as a rocksdb checksum error or assertion that looks like
os/bluestore/fastbmap_allocator_impl.h: 750: FAILED ceph_assert(available >= allocated)
or in some cases a rocksdb checksum error. It only affects BlueStore OSDs that have a separate 'db' or 'wal' device.
We have a fix[3] that is working its way through testing, and will expedite the next Nautilus point release (14.2.5) once it is ready.
If you are running 14.2.2 or 14.2.1 and use BlueStore OSDs with separate 'db' volumes, you should consider waiting to upgrade until 14.2.5 is released.
A big thank you to Igor Fedotov and several *extremely* helpful users who managed to reproduce and track down this problem!
sage
[1] https://tracker.ceph.com/issues/42223 [2] https://github.com/ceph/ceph/commit/096033b9d931312c0688c2eea7e14626bfde0ad7... [3] https://github.com/ceph/ceph/pull/31621 _______________________________________________ ceph-users mailing list -- ceph-users@ceph.io To unsubscribe send an email to ceph-users-leave@ceph.io
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