Hello Neil:
Sorry for the late reponse (busy at other stuff)
>
> If I'm interpreting your numbers correctly, it is just an occasional single
> write that is slow - not a series of writes during a one second interval that
> are each slow. It would help if you could confirm that.
>
No.
"output.txt" interpretation
- "max rw": max per-512KB-block write time in one second
- "speed": average write throughput in one second
"speed" reveals: It is an occasional single write-throughput-per-second is slow
>
> I don't know where you got 16 from
>
Sorry, I do the wrong math
>
> For some reason raid5 sometimes decides that it needs to pre-read the
> 'other' block to calculate parity rather than waiting for the other block
> to be written
>
>
Verifying using blktrace...
(Now I can reproduce the problem on "virtual machine + virtual disk",
with kernel 2.6.34)
>
> I'd be keen to hear about any further discoveries you make.
>
OK.
BTW, can you reproduce the problem and help debug on this ?
My debugging process will very slow (not familiar with RAID code)
Thanks
Eddy
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