On Tue, Feb 13, 2018 at 8:41 AM Graham Allan <gta@xxxxxxx> wrote:
I'm replying to myself here, but it's probably worth mentioning that
after this started, I did bring back the failed host, though with "ceph
osd weight 0" to avoid more data movement.
For inconsistent pgs containing unfound objects, the output of "ceph pg
<n> query" does then show the original osd being queried for objects,
and indeed if I dig through the filesystem I find the same 0-byte files
dated from 2015-2016.
This strongly implies to me that data loss occurred a long time in the
past and is not related to the osd host going down - this only triggered
the problem being found.
I would assume that too, but unless you had scrubbing disabled then it should have been discovered long ago; I don’t understand how it could have stayed hidden. Did you change any other settings recently?
Or, what is this EC pool being used for, and what are the EC settings? Having a bunch of empty files is not surprising if the objects are smaller than the chunk/stripe size — then just the primary and the parity locations would actually have data for them.
Graham
On 02/12/2018 06:26 PM, Graham Allan wrote:
> Hi,
>
> For the past few weeks I've been seeing a large number of pgs on our
> main erasure coded pool being flagged inconsistent, followed by them
> becoming active+recovery_wait+inconsistent with unfound objects. The
> cluster is currently running luminous 12.2.2 but has in the past also
> run its way through firefly, hammer and jewel.
>
> Here's a sample object from "ceph pg list_missing" (there are 150
> unfound objects in this particular pg):
>
> ceph health detail shows:
>> pg 70.467 is stuck unclean for 1004525.715896, current state
>> active+recovery_wait+inconsistent, last acting [449,233,336,323,259,193]
>
> ceph pg 70.467 list_missing:
>> {
>> "oid": {
>> "oid":
>> "default.323253.6_20150226/Downloads/linux-nvme-HEAD-5aa2ffa/include/config/via/fir.h",
>>
>> "key": "",
>> "snapid": -2,
>> "hash": 628294759,
>> "max": 0,
>> "pool": 70,
>> "namespace": ""
>> },
>> "need": "73222'132227",
>> "have": "0'0",
>> "flags": "none",
>> "locations": [
>> "193(5)",
>> "259(4)",
>> "449(0)"
>> ]
>> },
>
> When I trace through the filesystem on each OSD, I find the associated
> file present on each OSD but with size 0 bytes.
>
> Interestingly, for the 3 OSDs for which "list_missing" shows locations
> above (193,259,449), the timestamp of the 0-byte file is recent (within
> last few weeks). For the other 3 OSDs (233,336,323), it's in the distant
> past (08/2015 and 02/2016).
>
> All the unfound objects I've checked on this pg show the same pattern,
> along with the "have" epoch showing as "0'0".
>
> Other than the potential data loss being disturbing, I wonder why this
> showed up so suddenly?
>
> It seems to have been triggered by one OSD host failing over a long
> weekend. By the time we looked at it on Monday, the cluster had
> re-balanced enough data that I decided to simply leave it - we had long
> wanted to evacuate a first host to convert to a newer OS release, as
> well as Bluestore. Perhaps this was a bad choice, but the cluster
> recovery appeared to be proceeding normally, and was apparently complete
> a few days later. It was only around a week later that the unfound
> objects started.
>
> All the unfound object file fragments I've tracked down so far have
> their older members with timestamps in the same mid-2015 to mid-2016
> period. I could be wrong but this really seems like a long-standing
> problem has just been unearthed. I wonder if it could be connected to
> this thread from early 2016, concerning a problem on the same cluster:
>
> http://lists.ceph.com/pipermail/ceph-users-ceph.com/2016-March/008120.html
>
> It's a long thread, but the 0-byte files sound very like the "orphaned
> files" in that thread - related to performing a directory split while
> handling links on a filename with the special long filename handling...
>
> http://lists.ceph.com/pipermail/ceph-users-ceph.com/2016-March/008317.html
>
> However unlike that thread, I'm not finding any other files with
> duplicate names in the hierarchy.
>
> I'm not sure there's much else I can do besides record the names of any
> unfound objects before resorting to "mark_unfound_lost delete" - any
> suggestions for further research?
>
> Thanks,
>
> Graham
--
Graham Allan
Minnesota Supercomputing Institute - gta@xxxxxxx
_______________________________________________
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
