Hi all,
We are running a small cluster with three nodes and 6-8 OSDs each.
The OSDs are SSDs with sizes from 2 to 4 TB. Crush map is configured so
all data is replicated to each node.
The Ceph version is Ceph 15.2.6.
Today I deleted 4 Snapshots of the same two 400GB and 500GB rbd volumes.
Shortly after issuing the delete, I noticed the cluster became
unresponsive to an extend where almost all our services went down due
high IO latency.
After a while, I noticed about 20 active snaptrim tasks + another 200 or
so snaptrim_wait.
I tried setting
osd_snap_trim_sleep to 3,
osd_pg_max_concurrent_snap_trims to 1
rbd_balance_snap_reads to true,
rbd_localize_snap_reads to true
Still the only way to make the cluster responsive again was to set
osd_pg_max_concurrent_snap_trims to 0 and thus disable snaptrimming.
I tried a few other options, but whenever snaptrims are running for a
significant number of PGs, the cluster becomes completely unusable.
Are there any other options to throttle snaptrimming for that I haven't
tried, yet?
Thank you,
Pascal
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