On Thu, Oct 8, 2015 at 10:21 AM, Burkhard Linke
<Burkhard.Linke@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> Hi,
>
> I've moved all files from a CephFS data pool (EC pool with frontend cache
> tier) in order to remove the pool completely.
>
> Some objects are left in the pools ('ceph df' output of the affected pools):
>
> cephfs_ec_data 19 7565k 0 66288G 13
>
> Listing the objects and the readable part of their 'parent' attribute:
>
> # for obj in $(rados -p cephfs_ec_data ls); do echo $obj; rados -p
> cephfs_ec_data getxattr parent | strings; done
> 10000f6119f.00000000
> 10000f6119f
> stray9
> 10000f63fe5.00000000
> 10000f6119f
> stray9
> 10000f61196.00000000
> 10000f6119f
> stray9
> .......
>
> The names are valid CephFS object names. But the parent attribute does not
> contain the path of file the object belongs to; instead the string 'stray'
> is the only useful information (without dissecting the binary content of the
> parent attribute).
>
> What are those objects and is it safe to remove the pool in this state?
Well, they're strays :-)
You get stray dentries when you unlink files. They hang around either
until the inode is ready to be purged, or if there are hard links then
they hang around until something prompts ceph to "reintegrate" the
stray into a new path.
You don't say what version you're running, so it's possible you're
running an older version (pre hammer, I think) where you're
experiencing either a bug holding up deletion (we've had a few) or a
bug preventing reintegration (we had one of those too). The bugs
holding up deletion can usually be worked around with some client
and/or mds restarts.
It isn't safe to remove the pool in this state. The MDS is likely to
crash if it eventually gets around to trying to purge these files.
John
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