Re: waiting for sub ops

[Stefan Priebe - Profihost AG <s.priebe@profihost.ag>]

>> 1.) th osd bench shows 150MB/s per osd
>> 2.) iperf shows constant 930Mbit/s per eth
>> 3.) when i write 16GB with dd to the ceph mount i see spikes to 450Mbit/ and
>> drops to 90kb/s for long periods of time. The overall dd speed is then
>> 40Mbit/s
> 
> We were doing some btrfs performance testing this week and seeing similar 
> bursty behavior.  (See my May 7th performance on btrfs email for some 
> out-of-context detail.)  It currently looks like the workload we're 
> presenting to the fs is resulting in non-optimal writeout, but we haven't 
> figured out yet how we can improve that or nailed down the source for the 
> burstiness.  How that some of the inktank launch stuff is out of the way 
> we'll be picking it up again and continuing to work on that this week.
> 
> If you're interested in getting involved, ping nhm in #ceph.  It would be 
> interesting to capture a block trace from your environment and see if 
> what you're seeing is what we're seeing!
Thank for your information - we've holdays in germany from thursday on
and i won't be available. So thanks for the offer.

But if you want i can provide a trace. Just tell me how i can produce one.

Thanks!

Stefan