Re: Large OSD omap directories (LevelDBs)

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> Your RGW buckets, how many objects in them, and do they have the index
> sharded?

> I know we have some very large & old buckets (10M+ RGW objects in a
> single bucket), with correspondingly large OMAPs wherever that bucket
> index is living (sufficently large that trying to list the entire thing
> online is fruitless). ceph's pgmap status says we have 2G RADOS objects
> however, and you're only at 61M RADOS objects.


According to radosgw-admin bucket stats the most populous bucket contains 568101 objects. There is no index sharding. The default.rgw.buckets.data pool contains 4162566 objects, I think striping is done by default for 4MB sizes stripes.

Bear in mind RGW is a small use case for us currently.
Most of the data lives in a pool that is accessed by specialized servers that have plugins based on libradosstriper. That pool stores around 1.8 PB in 32920055 objects.

One thing of note is that we have this:
filestore_xattr_use_omap=1
in our ceph.conf and libradosstriper makes use of xattrs for striping metadata and locking mechanisms.

This seems to have been removed some time ago but the question is could have any effect? This cluster was built in January and ran Jewel initially.

I do see the xattrs in XFS but a sampling of an omap dir from an OSD showed like there might be some xattrs in there too.

I'm going to try restarting an OSD with a big omap and also extracting a copy of one for further inspection.
It seems to me like they might not be cleaning up old data. I'm fairly certain an active cluster would've compacted enough for 3 month old SSTs to go away.

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