[lustre-discuss] Slow release of inodes on OST

[Andreas Dilger]

On Feb 4, 2020, at 07:23, Åke Sandgren <ake.sandgren at hpc2n.umu.se<mailto:ake.sandgren at hpc2n.umu.se>> wrote:

When I create a large number of files on an OST and then remove them,
the used inode count on the OST decreases very slowly, it takes several
hours for it to go from 3M to the correct ~10k.

(I'm running the io500 test suite)

Is there something I can do to make it release them faster?
Right now it has gone from 3M to 1.5M in 6 hours, (lfs df -i).

It this the object count or the file count?  Are you possibly using a lot of
stripes on the files being deleted that is multiplying the work needed?

These are SSD based OST's in case it matters.

The MDS controls the destroy of the OST objects, so there is a rate
limit, but ~700/s seems low to me, especially for SSD OSTs.

You could check "lctl get_param osp.*.sync*" on the MDS to see how
many destroys are pending.  Also, increasing osp.*.max_rpcs_in_flight
on the MDS might speed this up?  It should default to 32 per OST on
the MDS vs. default 8 for clients

Cheers, Andreas
--
Andreas Dilger
Principal Lustre Architect
Whamcloud






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