Hi Guys,
I've been tracking down some performance issues over the past month with
our internal test nodes and believe I have narrowed it down to something
related to Ubuntu Oneiric. Tests done on nodes running Ubuntu Precise
are significantly faster.
One of the major differences between the releases is the support for
syncfs in libc. Theoretically this shouldn't have a big effect on btrfs
so I'm not totally sure that this is the culprit. Having said that,
previous tests showed good SSD performance on Oneiric leading me to
believe the lower latency mitigates the effect. Some of spinning disk
seekwatcher results for Oneiric are quite strange with long periods of
inactivity on the OSD data disks.
I wanted to post these results for those of you who have had performance
problems in the past. If you are continuing to have issues, you may
want to try testing on precise and see if you notice any changes. It is
possible that all of this could be specific to our internal testing
nodes, so I wouldn't mind hearing if other people have seen similar
behavior.
These tests were done using rados bench with 16 concurrent requests.
There are two nodes that each have a single 7200rpm OSD data disk and
journal on a second 7200rpm disk. Replication is set at the default
level (2). Kernel is 3.4 in all cases.
Here's a run down (Numbers are MB/s)
4KB Requests
BTRFS EXT4 XFS
Ceph 0.46/Oneiric: 0.073 0.694 0.723
Ceph 0.46/Precise: 2.15 2.031 1.546
Ceph 0.47.2/Oneiric: 1.072 0.836 0.749
Ceph 0.47.2/Precise: 2.566 2.579 1.498
128KB Requests:
BTRFS EXT4 XFS
Ceph 0.46/Oneiric: 11.874 20.066 12.641
Ceph 0.46/Precise: 49.304 39.736 38.982
Ceph 0.47.2/Oneiric: 13.81 19.05 12.739
Ceph 0.47.2/Precise: 47.943 49.655 36.764
4MB Requests:
BTRFS EXT4 XFS
Ceph 0.46/Oneiric: 110.202 26.58 15.445
Ceph 0.46/Precise: 135.975 128.759 106.426
Ceph 0.47.2/Oneiric: 91.337 46.277 23.897
Ceph 0.47.2/Precise: 136.906 134.955 106.545
I've posted seekwatcher results for all of the tests:
Ceph 0.46/Oneiric: http://nhm.ceph.com/movies/sprint/test2
Ceph 0.46/Precise: http://nhm.ceph.com/movies/sprint/test3
Ceph 0.47.2/Oneiric: http://nhm.ceph.com/movies/sprint/test4
Ceph 0.47.2/Precise: http://nhm.ceph.com/movies/sprint/test5
Mark
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