Re: Slow Soft-RAID 5 performance

[Rui Santos <rsantos@grupopie.com>]

koan wrote:
> 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.

Hi Koan,

Yes, I'm sure... Those 128K chunk was my initial setup, before the
enlightenment from http://tldp.org/HOWTO/Software-RAID-HOWTO-5.html
My reported test setup is by using 256K chunk.

>
>
>
> 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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