On Wed, Mar 31, 2021 at 6:46 PM Patrick Donnelly <pdonnell@redhat.com> wrote:
Hello Yongseok,
On Wed, Mar 31, 2021 at 1:13 AM Yongseok Oh <yongseok.oh@linecorp.com> wrote:
...
A few things I have analyzed - Rejoining process consumes a considerable amount of time. That's a known issue. (Sometimes respawning MDS happened. Increasing mds_heartbeat_grace doesn't help.)
Please turn up logging to:
debug_mds = 5
to get an idea what the MDS is doing when respawn occurs.
If it helps, here is a log with 2/5 from a recent failover which took 3.5 minutes: https://termbin.com/b022 This is 14.2.11 with the optimized recall/cache tuning. Indeed rejoin is always the longest step -- even with cephfs_metadata on SSDs. These MDSs had the cache limit set to 8GB, and you can see that the rejoining MDS needed 56GB while booting. I haven't had a chance to test the rejoin/openfiletables optimizations yet. (https://github.com/ceph/ceph/pull/37383) But I had understood that this is intended to decrease that rejoin memory usage -- will it also speed things up? -- dan