Stripe sizes with gstripe
David Kelly
dkelly at hiwaay.net
Fri Jun 13 14:28:12 UTC 2008
On Fri, Jun 13, 2008 at 09:08:48AM +0200, Wojciech Puchar wrote:
> >>Does gstripe read an entire stripe at a time? If so, why do that instead
> >>of
> >>just reading a few requested blocks? If not, then is there any advantage
> >>to large stripes?
> >
> >Apparently it won't read anything larger than your stripe size which
> >defaults to a miserable 4k.
>
>
> depending from what's needed, but unless i need just huge linear transfer,
> i set stripe size to something huge, like 256MB.
>
> then single read is rarely split on 2 disks, while multiple reads have
> good chances to touch different drives
Come to think of it I didn't try setting the stripe size larger than the
ATA max transaction size of 128k.
Still, I don't understand what is going on when I use md5(1) on a
gigabyte file hosted on a gstripe partition with 128k stripes that
"systat -v" reports transactions are usually between 42k and 43k each?
On a non-striped filesystem the same operation runs 126k to 127k
transfers.
Transfer bandwidth seems to be limited by the number of transactions per
second more than the size of the transaction.
--
David Kelly N4HHE, dkelly at HiWAAY.net
========================================================================
Whom computers would destroy, they must first drive mad.
More information about the freebsd-questions
mailing list