I don't think there's a way of getting the prefix from the cluster at this point.
If the deleted image was a similar size to the example you've given, you will likely have had objects on every OSD. If this data is absolutely critical you need to stop your cluster immediately or make copies of all the drives with something like dd. If you've never deleted any other rbd images and assuming you can recover data with names, you may be able to find the rbd objects. On Mon, Aug 8, 2016 at 7:28 PM, Georgios Dimitrakakis <gior...@acmac.uoc.gr> wrote: > Hi, >>> >>> >>> On 08.08.2016 10:50, Georgios Dimitrakakis wrote: >>> >>>> Hi, >>>>> >>>>> >>>>> On 08.08.2016 09:58, Georgios Dimitrakakis wrote: >>>>> >>>>>> Dear all, >>>>>> >>>>>> I would like your help with an emergency issue but first let me >>>>>> describe our environment. >>>>>> >>>>>> Our environment consists of 2OSD nodes with 10x 2TB HDDs each and >>>>>> 3MON nodes (2 of them are the OSD nodes as well) all with ceph version >>>>>> 0.80.9 (b5a67f0e1d15385bc0d60a6da6e7fc810bde6047) >>>>>> >>>>>> This environment provides RBD volumes to an OpenStack Icehouse >>>>>> installation. >>>>>> >>>>>> Although not a state of the art environment is working well and >>>>>> within our expectations. >>>>>> >>>>>> The issue now is that one of our users accidentally deleted one of >>>>>> the volumes without keeping its data first! >>>>>> >>>>>> Is there any way (since the data are considered critical and very >>>>>> important) to recover them from CEPH? >>>>>> >>>>> >>>>> Short answer: no >>>>> >>>>> Long answer: no, but.... >>>>> >>>>> Consider the way Ceph stores data... each RBD is striped into chunks >>>>> (RADOS objects with 4MB size by default); the chunks are distributed >>>>> among the OSDs with the configured number of replicates (probably two >>>>> in your case since you use 2 OSD hosts). RBD uses thin provisioning, >>>>> so chunks are allocated upon first write access. >>>>> If an RBD is deleted all of its chunks are deleted on the >>>>> corresponding OSDs. If you want to recover a deleted RBD, you need to >>>>> recover all individual chunks. Whether this is possible depends on >>>>> your filesystem and whether the space of a former chunk is already >>>>> assigned to other RADOS objects. The RADOS object names are composed >>>>> of the RBD name and the offset position of the chunk, so if an >>>>> undelete mechanism exists for the OSDs' filesystem, you have to be >>>>> able to recover file by their filename, otherwise you might end up >>>>> mixing the content of various deleted RBDs. Due to the thin >>>>> provisioning there might be some chunks missing (e.g. never allocated >>>>> before). >>>>> >>>>> Given the fact that >>>>> - you probably use XFS on the OSDs since it is the preferred >>>>> filesystem for OSDs (there is RDR-XFS, but I've never had to use it) >>>>> - you would need to stop the complete ceph cluster (recovery tools do >>>>> not work on mounted filesystems) >>>>> - your cluster has been in use after the RBD was deleted and thus >>>>> parts of its former space might already have been overwritten >>>>> (replication might help you here, since there are two OSDs to try) >>>>> - XFS undelete does not work well on fragmented files (and OSDs tend >>>>> to introduce fragmentation...) >>>>> >>>>> the answer is no, since it might not be feasible and the chance of >>>>> success are way too low. >>>>> >>>>> If you want to spend time on it I would propose the stop the ceph >>>>> cluster as soon as possible, create copies of all involved OSDs, start >>>>> the cluster again and attempt the recovery on the copies. >>>>> >>>>> Regards, >>>>> Burkhard >>>>> >>>> >>>> Hi! Thanks for the info...I understand that this is a very difficult >>>> and probably not feasible task but in case I need to try a recovery what >>>> other info should I need? Can I somehow find out on which OSDs the specific >>>> data were stored and minimize my search there? >>>> Any ideas on how should I proceed? >>>> >>> First of all you need to know the exact object names for the RADOS >>> objects. As mentioned before, the name is composed of the RBD name and >>> an offset. >>> >>> In case of OpenStack, there are three different patterns for RBD names: >>> >>> <GUID>, e.g. 50f2a0bd-15b1-4dbb-8d1f-fc43ce535f13 >>> for glance images, >>> <GUID_disk>, e.g. 9aec1f45-9053-461e-b176-c65c25a48794_disk for nova >>> images >>> <volume_GUID>, e.g. volume-0ca52f58-7e75-4b21-8b0f-39cbcd431c42 for >>> cinder volumes >>> >>> (not considering snapshots etc, which might use different patterns) >>> >>> The RBD chunks are created using a certain prefix (using examples >>> from our openstack setup): >>> >>> # rbd -p os-images info 8fa3d9eb-91ed-4c60-9550-a62f34aed014 >>> rbd image '8fa3d9eb-91ed-4c60-9550-a62f34aed014': >>> size 446 MB in 56 objects >>> order 23 (8192 kB objects) >>> block_name_prefix: rbd_data.30e57d54dea573 >>> format: 2 >>> features: layering, striping >>> flags: >>> stripe unit: 8192 kB >>> stripe count: 1 >>> >>> # rados -p os-images ls | grep rbd_data.30e57d54dea573 >>> rbd_data.30e57d54dea573.0000000000000015 >>> rbd_data.30e57d54dea573.0000000000000008 >>> rbd_data.30e57d54dea573.000000000000000a >>> rbd_data.30e57d54dea573.000000000000002d >>> rbd_data.30e57d54dea573.0000000000000032 >>> >>> I don't know how whether the prefix is derived from some other >>> information, but the recover the RBD you definitely need it. >>> >>> _If_ you are able to recover the prefix, you can use 'ceph osd map' >>> to find the OSDs for each chunk: >>> >>> # ceph osd map os-images rbd_data.30e57d54dea573.000000000000001a >>> osdmap e418590 pool 'os-images' (38) object >>> 'rbd_data.30e57d54dea573.000000000000001a' -> pg 38.d5d81d65 (38.65) >>> -> up ([45,17,108], p45) acting ([45,17,108], p45) >>> >>> With 20 OSDs in your case you will likely have to process all of them >>> if the RBD has a size of several GBs. >>> >>> Regards, >>> Burkhard >>> >> >> >> Is it possible to get the prefix if the RBD has been deleted >> already?? Is this info somewhere stored? Can I retrieve it with >> another way besides "rbd info"? Because when I try to get it using the >> "rbd info" command unfortunately I am getting the following error: >> >> "librbd::ImageCtx: error finding header: (2) No such file or directory" >> >> >> Any ideas? >> >> Best regards, >> >> G. >> > > > Here are some more info from the cluster: > > $ ceph df > GLOBAL: > SIZE AVAIL RAW USED %RAW USED > 74373G 72011G 2362G 3.18 > POOLS: > NAME ID USED %USED MAX AVAIL OBJECTS > data 3 0 0 35849G 0 > metadata 4 1884 0 35849G 20 > rbd 5 0 0 35849G 0 > .rgw 6 1374 0 35849G 8 > .rgw.control 7 0 0 35849G 8 > .rgw.gc 8 0 0 35849G 32 > .log 9 0 0 35849G 0 > .intent-log 10 0 0 35849G 0 > .usage 11 0 0 35849G 3 > .users 12 33 0 35849G 3 > .users.email 13 22 0 35849G 2 > .users.swift 14 22 0 35849G 2 > .users.uid 15 985 0 35849G 4 > .rgw.root 16 840 0 35849G 3 > .rgw.buckets.index 17 0 0 35849G 4 > .rgw.buckets 18 170G 0.23 35849G 810128 > .rgw.buckets.extra 19 0 0 35849G 1 > volumes 20 1004G 1.35 35849G 262613 > > > > Obviously the RBD volumes provided to OpenStack are stored on the > "volumes" pool , so trying to > figure out the prefix for the volume in question > "volume-a490aa0c-6957-4ea2-bb5b-e4054d3765ad" produces the following: > > $ rbd -p volumes info volume-a490aa0c-6957-4ea2-bb5b-e4054d3765ad > rbd: error opening image volume-a490aa0c-6957-4ea2-bb5b-e4054d3765ad: (2) > No such file or directory > 2016-08-09 03:04:56.250977 7fa9ba1ca760 -1 librbd::ImageCtx: error finding > header: (2) No such file or directory > > > On the other hand for a volume that already exists and is working normally > since I get the following: > > $ rbd -p volumes info volume-2383fc3a-2b6f-49b4-a3f5-f840569edb73 > rbd image 'volume-2383fc3a-2b6f-49b4-a3f5-f840569edb73': > size 500 GB in 128000 objects > order 22 (4096 kB objects) > block_name_prefix: rbd_data.fb1bb3136c3ec > format: 2 > features: layering > > and can also get the OSD mapping etc. > > Does that mean that there is no way to find out on which OSDs the deleted > volume was placed? > If that's the case then it's not possible to recover the data...Am I > right??? > > Any other ideas people??? > > Looking forward for your comments...please... > > > > Best regards, > > G. > _______________________________________________ > ceph-users mailing list > ceph-users@lists.ceph.com > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >
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