I think I had previously mentioned that I am interested in using RBD for
data backing a database. With the recent notable improvements in IO
performance for smaller block sizes that came with 0.50 and 0.51
versions I decided to do some benchmarking with Postgresql.
So here it is:
System : 4x (hyperthread) i3 3.3 Ghz 8G, 2x 128G Crucial M4
Ceph 0.51, 1x osd on 1 M4, 20G journal on the other, ext4 filesystems
Postgresql 9.2 with minimal tuning (shared_buffers = 1G,
checkpoint_segments = 128)
1x RBD for postgres data, 1x RBD for postgres transaction log, ext4
filesystems
Scale 300 (approx 5G)
connections | tx per second
------------+--------------
4 | 287
8 | 422
16 | 591
32 | 779
64 | 866
Now this is quite an acceptable result (previous attempts had maxed out
at 4 tx per sec). While it does not compare favourably with running the
same setup directly on the attached drives (4000 tx per sec with 64
connections), the difference is a 'mere' factor of 4 instead of orders
of magnitude, so I am greatly encouraged!
By default Postgreql does IO in 8K blocks using library functions read
and write - so this *was* a completely pessimal performance test - so it
is really nice to see how things are improving - keep up the good work!
Regards
Mark
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