Hi Erwan,
Out of curiosity did you look at the mempool stats at all? It's
pretty likely you'll run out of memory with 512MB given our current
defaults and the memory autotuner won't be able to keep up (it will do
it's best, but can't work miracles).
As per the ceph-nano project, the cluster is very simple with the
following configuration :
cluster:
id: b2eafdd3-ec87-4107-afaf-521980bb3d9e
health: HEALTH_OK
services:
mon: 1 daemons, quorum ceph-nano-travis-faa32aebf00b (age 2m)
mgr: ceph-nano-travis-faa32aebf00b(active, since 2m)
osd: 1 osds: 1 up (since 2m), 1 in (since 2m)
rgw: 1 daemon active
data:
pools: 5 pools, 40 pgs
objects: 174 objects, 1.6 KiB
usage: 1.0 GiB used, 9.0 GiB / 10 GiB avail
pgs: 40 active+clean
I'll save the mempool stats over time to see what is growing on the idle
case.
[...]
In any event, when I've tested OSDs with that little memory there's
been fairly dramatic performance impacts in a variety of ways
depending on what you change. In practice the minimum amount of
memory we can reasonable work with right now is probably around
1.5-2GB, and we do a lot better with 3-4GB+.
In the ceph-nano context, we don't really target performance.
