Ceph status HEALTH_WARN while adding an RGW Instance - rest

Question

I want to create ceph cluster and then connect to it through S3 RESTful api.
So, I've deployed ceph cluster (mimic 13.2.4) on "Ubuntu 16.04.5 LTS" with 3 OSD (one per each HDD 10Gb).
Using this tutorials:
1) http://docs.ceph.com/docs/mimic/start/quick-start-preflight/#ceph-deploy-setup
2) http://docs.ceph.com/docs/mimic/start/quick-ceph-deploy/
At this point, ceph status is OK:
root#ubuntu-srv:/home/slavik/my-cluster# ceph -s
cluster:
id: d7459118-8c16-451d-9774-d09f7a926d0e
health: HEALTH_OK
services:
mon: 1 daemons, quorum ubuntu-srv
mgr: ubuntu-srv(active)
osd: 3 osds: 3 up, 3 in
data:
pools: 0 pools, 0 pgs
objects: 0 objects, 0 B
usage: 3.0 GiB used, 27 GiB / 30 GiB avail
pgs:
3) "To use the Ceph Object Gateway component of Ceph, you must deploy an instance of RGW. Execute the following to create an new instance of RGW:"
root#ubuntu-srv:/home/slavik/my-cluster# ceph-deploy rgw create ubuntu-srv
....
[ceph_deploy.rgw][INFO ] The Ceph Object Gateway (RGW) is now running on host ubuntu-srv and default port 7480
root#ubuntu-srv:/home/slavik/my-cluster# ceph -s
cluster:
id: d7459118-8c16-451d-9774-d09f7a926d0e
health: HEALTH_WARN
too few PGs per OSD (2 < min 30)
services:
mon: 1 daemons, quorum ubuntu-srv
mgr: ubuntu-srv(active)
osd: 3 osds: 3 up, 3 in
data:
pools: 1 pools, 8 pgs
objects: 0 objects, 0 B
usage: 3.0 GiB used, 27 GiB / 30 GiB avail
pgs: 37.500% pgs unknown
62.500% pgs not active
5 creating+peering
3 unknown
Ceph status has been changed to HEALTH_WARN - why and how to resolve it?

Answer 1

Your issue is
health: HEALTH_WARN
too few PGs per OSD (2 < min 30)
Look at you current pg config by running:
ceph osd dump|grep pool
See what each pool is configured for pg count, then goto https://ceph.com/pgcalc/ to calculate what your pools should be configured for.
The warning is that you have a low number of pg's per osd, right now you have 2 per osd, where min should be 30