[OpenAFS] Expected performance
Tue, 17 May 2011 23:14:03 +0100
We have a 1.4.12 openafs server, which is a VM sitting on a SAN storage
(Xen based Oracle VM), having 2GB of ram and 4 vcpus.
After some test runs, we were a bit displeased with the obtained
Tests were made using dd, with files greater than the client cache size
forcing a sync after dd ended. (roughly what's observed here
Each test was performed in equal situation, with no concurrent access,
and each system was only performing the test at that time.
- Low performance and high discrepancy between test results
Transfer rates (only a few) hardly touched 30MB/s between the server and
a client sitting on the same network, connected via GB ethernet. Most of
the times that transfer rate is around 20MB/s, falling down to 13 or
14MB/s in some cases.
- Problem doesn't seem to be network related
After these findings, we then performed exactly the same tests on the
server machine, while acting as client of itself, i.e. with no physical
network involved. The outcome, sadly, was the same. We tried both with
and without jumbograms and we obtained roughly the same results, either
while using 2 machines (client/server) or only one machine.
- No concerning system load
We observed no major cpu activity, having fileserver reach around 30% of
cpu usage in some very short peaks. Memory was also fine all through the
- It's not the disks either
We also outruled disk bottleneck since on the same machines, using the
exact same type of storage we would get around 130MB/s while reading and
110MB/s while writing.
Another very weird thing was that reading transfers were (mostly) all
slower than writting.
Does anyone detect any kind of inconsistency in this scenario or were
our expectations a bit too high?
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