Re: massive 4k random read drop with next branch

[Mark Nelson <mark.nelson@inktank.com>]

On 04/27/2013 03:13 PM, Stefan Priebe wrote:
> Hello list,
>
> today i was testing next branch against bobtail using a testcluster. I
> upgraded this bobtail one to next branch.
>
> I used QEMU 1.4.1 with librdb (for next branch i applied josh writeback
> patch). My Testsystem had 5 Hosts with one OSD each and set replication
> to 2.
>
> All values where done with 8 jobs in parallel using fio in Qemu Guest.
>
> bobtail:
> rand 4k:  write: io=164316KB, bw=1783KB/s, iops=445, runt= 92136msec
> rand 4k:  read : io=1117MB, bw=12710KB/s, iops=3177, runt= 90028msec
> seq 4m:  write: io=8588MB, bw=97233KB/s, iops=23, runt= 90444msec
> seq 4m:  read : io=83616MB, bw=951227KB/s, iops=232, runt= 90013msec
>
> next branch:
>    write: io=177236KB, bw=1963KB/s, iops=490, runt= 90284msec
>    read : io=223628KB, bw=2408KB/s, iops=601, runt= 92875msec
>    write: io=25936MB, bw=294443KB/s, iops=71, runt= 90199msec
>    read : io=69856MB, bw=794585KB/s, iops=193, runt= 90025msec

Was everything else the same between the tests?  That does seem unusual. 
  If it's easy for you to switch between bobtail and next, could you try 
some 4k rados bench read tests to see if it's also happening there?

>
> Greets,
> Stefan
>
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