Re: Two identical systems, radically different performance

On 9.10.2012 01:03, Craig James wrote:
>
>
> On Mon, Oct 8, 2012 at 3:50 PM, Claudio Freire <klaussfreire(at)gmail(dot)com
> <mailto:klaussfreire(at)gmail(dot)com>> wrote:
>
> On Mon, Oct 8, 2012 at 7:48 PM, Craig James <cjames(at)emolecules(dot)com
> <mailto:cjames(at)emolecules(dot)com>> wrote:
> >> > # blockdev --getra /dev/sdb1
> >> > 256
> >>
> >>
> >> It's probably this. 256 is way too low to saturate your I/O system.
> >> Pump it up. I've found 8192 works nice for a system I have, 32000 I
> >> guess could work too.
> >
> >
> > But again ... the two systems are identical. This can't explain it.
>
> Is the read-ahead the same in both systems?
>
>
> Yes, as I said in the original reply (it got cut off from your reply):
> "Same on both servers."

And what about read-ahead settings on the controller? 3WARE used to have
a read-ahead settings on their own (usually there are three options -
read-ahead, no read-ahead and adaptive). Is this set to the same value
on both machines?

Tomas