[Openstack] Swift slow write performance

Rustam Aliyev rustam at code.az
Fri Dec 16 03:20:14 UTC 2011


I'm testing swift 1.4.4 setup with 4 nodes/zones on RHEL 5.7. I ran into 
the problem of slow writes. Using swift-bench we generated load, writing 
hundreds of 4K files. Results:
  - Writes - ~3 PUTs/sec (very slow)
  - Reads - ~25 GETs/sec (ok)

It's clear that writes are not limited by I/O. To prove that, I 
increased file size to 8K, 32K and 64K. In all cases, even with 64K, I 
had same result - 3 PUTs/sec.

In the logs of the object servers I can see that each PUT operation 
actually took around 0.3 sec which is inline with 3 PUTs/ sec reported 
by swift-bench.

Is that expected performance for such small cluster? Can I break down 
those 0.3 seconds spent for PUT operation to see where's bottleneck?

Any advice for troubleshooting this is welcome.


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