On 11/8/22 21:20, Mark Nelson wrote:
Hi Folks,
I thought I would mention that I've released a couple of performance
articles on the Ceph blog recently that might be of interest to people:
For sure, thanks a lot, it's really informative!
Can we also ask for special requests? One of the things that would help
us (and CephFS users in general) is how performance of CephFS for small
files (~512 bytes, 2k up to say 64K) is impacted by the amount of PGs a
CephFS metadata pool has.
Question that might be answered:
- does it help to provision more PGs for workloads that rely heavily on
OMAP usage by the MDS (or is RocksDB the bottleneck in all cases)?
Tests that might be useful:
- rsync (single threaded, worst case)
- fio random read / write tests with varying io depths and threads
- The CephFS devs might know some performance tests in this context
One of the tricky things with doing these benchmarks, is that the PG
placement over the OSDs might heavily impact performance all by itself,
as primary PGs are not placed in the same way with different amount of
PGs in the pool. Therefore, ideally, the primaries are balanced as
evenly possible. I'm eagerly awaiting the Ceph virtual 2022 talk "New
workload balancer in Ceph". Having the primaries balanced before these
benchmarks run seems to be a prerequisite to do a "apples to apples"
comparison.
Gr. Stefan
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