Hi,
This is similar to another thread running right now, but since our
current setup is completely different from the one described in the
other thread, I thought it may be better to start a new one.
We are running Ceph Firefly 0.80.8 (soon to be upgraded to 0.80.9). We
have 6 OSD hosts with 16 OSD each (so a total of 96 OSDs). Each OSD is a
Samsung SSD 840 EVO on which I can reach write speeds of roughly 400
MB/sec, plugged in jbod on a controller that can theoretically transfer
at 6gb/sec. All of that is linked to openstack compute nodes on two
bonded 10gbps links (so a max transfer rate of 20 gbps).
When I run rados bench from the compute nodes, I reach the network cap
in read speed. However, write speeds are vastly inferior, reaching about
920 MB/sec. If I have 4 compute nodes running the write benchmark at the
same time, I can see the number plummet to 350 MB/sec . For our planned
usage, we find it to be rather slow, considering we will run a high
number of virtual machines in there.
Of course, the first thing to do would be to transfer the journal on
faster drives. However, these are SSDs we're talking about. We don't
really have access to faster drives. I must find a way to get better
write speeds. Thus, I am looking for suggestions as to how to make it
faster.
I have also thought of options myself like:
-Upgrading to the latest stable hammer version (would that really give
me a big performance increase?)
-Crush map modifications? (this is a long shot, but I'm still using the
default crush map, maybe there's a change there I could make to improve
performances)
Any suggestions as to anything else I can tweak would be strongly
appreciated.
For reference, here's part of my ceph.conf:
[global]
auth_service_required = cephx
filestore_xattr_use_omap = true
auth_client_required = cephx
auth_cluster_required = cephx
osd pool default size = 3
osd pg bits = 12
osd pgp bits = 12
osd pool default pg num = 800
osd pool default pgp num = 800
[client]
rbd cache = true
rbd cache writethrough until flush = true
[osd]
filestore_fd_cache_size = 1000000
filestore_omap_header_cache_size = 1000000
filestore_fd_cache_random = true
filestore_queue_max_ops = 5000
journal_queue_max_ops = 1000000
max_open_files = 1000000
osd journal size = 10000
--
======================
Jean-Philippe Méthot
Administrateur système / System administrator
GloboTech Communications
Phone: 1-514-907-0050
Toll Free: 1-(888)-GTCOMM1
Fax: 1-(514)-907-0750
jpmethot@xxxxxxxxxx
http://www.gtcomm.net
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