Re: poor OSD performance using kernel 3.4

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

Can really nobody help?

Am 25.05.2012 17:47, schrieb Alexandre DERUMIER:
> Hi Stephan,
> Do you have same performance with read ?

Read is fine for both versions see here:

3.0.30

Write:
Total time run:        30.872357
Total writes made:     1095
Write size:            4194304
Bandwidth (MB/sec):    141.874

Average Latency:       0.450187
Max latency:           2.00672
Min latency:           0.091783

Read:
Total time run:        22.907021
Total reads made:     1095
Read size:            4194304
Bandwidth (MB/sec):    191.208

Average Latency:       0.333954
Max latency:           1.71987
Min latency:           0.041373

3.4.0

Write:
Total time run:        124.573247
Total writes made:     647
Write size:            4194304
Bandwidth (MB/sec):    20.775

Average Latency:       3.08058
Max latency:           65.2522
Min latency:           0.089587

Read:
Total time run:        13.191562
Total reads made:     647
Read size:            4194304
Bandwidth (MB/sec):    196.186

Average Latency:       0.322895
Max latency:           1.22392
Min latency:           0.043784


> Did you have done some iostats ?
Yes - I/O is heavily jumping between 0 and 60MB/s but of the time it's 0 
or around 10MB/s.

> how much time to flush from journal to disks ?
I don't know how to measure this. As ceph starts to write to journal and 
disk in parallel and tmpfs isn't even shown in iostat.

Greets,
Stefan