Re: RAID-0 read perf. decrease after 2.4.20

[Mikael Johansson]

Hello again!

Finally had time to test this on IDE, "better late than even later"...

On Thu, 18 Dec 2003, Martin Knoblauch wrote:

> > >  Just some feedback:
> > >
> > > echo 511 > /proc/sys/vm/max-readahead
> > >
> > >  brings back the read performance of my 30 disks on 4 controller
> > > LVM/RAID0.
> >
> > Great.
> >
>
>  Indeed :-) Just to clarify - the modification of max-readahead was
> sufficient to "fix" the observed read performance degradation. I did
> not apply (or reverse) anything on top of 2.4.22.
>
>  Actually 255 would have been sufficient, 511 proved to be a small bit
> better :-))

The "max-readahead" does not seem to affect IDE-RAID, at least not with
the 2.4.27-pre6 I just compiled on two machines. So the problem still
exists, read speed on 2.4.20-ac2 is almost twice as fast as on later
kernels :-/

Have a nice summer,
    Mikael J.
    http://www.helsinki.fi/~mpjohans/
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