Matthias Dahl <ml_linux_raid@xxxxxxxxxxxxxx> writes:
> Hi.
>
> On Saturday 08 August 2009 09:56:59 you wrote:
>
>> But each stripe only holds 128k of data. You have to align to that.
>
> I beg to differ. There are two data chunks and one parity chunk, thus a whole
> stripe is 192k long if you've a 64k chunk size. If you align to 128k and you
> put e.g. ext4 on it with the correct fs stride and stripe-width settings,
> you'll probably end up with worse performance since you start in the middle of
> a stripe even though properly aligned to a chunk boundary. Or am I totally on
> the wrong track here...?!
Yes you are. The filesystem will never ever see the parity block of a
stripe. It only ever sees the 128k data. Writing 128k data will write
a full stripe of 192k to disk.
MfG
Goswin
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