Re: Slow Soft-RAID 5 performance

[koan <koan00@gmail.com>]

Are you sure about that chunk size? In you initial posting you show
/proc/mdstat reporting:

"md2 : active raid5 sdc3[2] sda3[0] sdb3[1]
      780083968 blocks level 5, 128k chunk, algorithm 2 [3/3] [UUU]"

Which would seem to state a 128K chunk, and thus with a 4k block size
you would need a stride of 32.



On 7/18/07, Rui Santos <rsantos@grupopie.com> wrote:
> koan wrote:
> > How did you create the ext3 filesystem?
>
> The chunk_size is at 256KB, ext3 block size is 4k. I believe the correct
> option that should be passed trough to --stride is 64.
> Am I correct ?
>
> I've also tested ( after sending my first report ) with xfs.
> I've also increases readahead to 65535 on all HD's
> I've also increases the stripe_cache_size to 16384.
>
> I can now get ~100MB/sec...
>
> >
> > Did you use the appropriate --stride option as noted here:
> > http://tldp.org/HOWTO/Software-RAID-HOWTO-5.html (#5.11)
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