Hello!
I'm testing small CEPH pool consists of some SSD drives (without any
spinners). Ceph version is 0.67.4. Seems like write performance of this
configuration is not so good as possible, when I testing it with small
block size (4k).
Pool configuration:
2 mons on separated hosts, one host with two OSD. First partition of
each disk is used for journal and has 20Gb size, second is formatted as
XFS and used for data (mount options:
rw,noexec,nodev,noatime,nodiratime,inode64). 20% of space left
unformatted. Journal aio and dio turned on.
Each disk has about 15k IOPS with 4k blocks, iodepth 1 and 50k IOPS with
4k block, iodepth 16 (tested with fio). Linear throughput of disks is
about 420Mb/s. Network throughput is 1Gbit/s.
I use rbd pool with size 1 and want this pool to act like RAID0 at this
time.
Virtual machine (QEMU/KVM) on separated host is configured to use 100Gb
RBD as second disk. Fio running in this machine (iodepth 16, buffered=0,
direct=1, libaio, 4k randwrite) shows about 2.5-3k IOPS.
Multiple quests with the same configuration shows similar summary
result. Local kernel RBD on host with OSD also shows about 2-2.5k IOPS.
Latency is about 7ms. I also tried to pre-fill RBD without any results.
Atop shows about 90% disks utilization during tests. CPU utilization is
about 400% (2x Xeon E5504 is installed on ceph node). There is a lot of
free memory on host. Blktrace shows that about 4k operations (4k to
about 40k bytes) completing every second on every disk. OSD throughput
is about 30 MB/s.
I expected to see about 2 x 50k/4 = 20-30k IOPS on RBD, so is that too
optimistic for CEPH with such load or if I missed up something important?
I also tried to use one disk as journal (20GB, last space left
unformatted) and configure the next disk as OSD, this configuration have
shown almost the same result.
Playing with some osd/filestore/journal options with admin socket ended
with no result.
Please, tell me am I wrong with this setup? Or should I use more disks
to get better performance with small concurrent writes? Or is ceph
optimized for work with slow spinners and shouldn't be used with SSD
disk only?
Thank you very much in advance!
My ceph configuration:
ceph.conf
==========================================================================
[global]
auth cluster required = none
auth service required = none
auth client required = none
[client]
rbd cache = true
rbd cache max dirty = 0
[osd]
osd journal aio = true
osd max backfills = 4
osd recovery max active = 1
filestore max sync interval = 5
[mon.1]
host = ceph1
mon addr = 10.10.0.1:6789
[mon.2]
host = ceph2
mon addr = 10.10.0.2:6789
[osd.72]
host = ceph7
devs = /dev/sdd2
osd journal = /dev/sdd1
[osd.73]
host = ceph7
devs = /dev/sde2
osd journal = /dev/sde1
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