Re: RAID-0 read perf. decrease after 2.4.20

[Joshua Schmidlkofer <kernel@pacrimopen.com>]

On Mon, 2003-11-24 at 02:05, Martin Knoblauch wrote:
> >Hello All!
> >
> >Has anyone else experienced a drastic drop in read performance on
> >software
> >RAID-0 with post 2.4.20 kernels? We have a few Athlon XP's here at our
> >lab with double IDE disks on different channels set up as RAID-0. Some
> >bonnie++ benchmark results with various kernels, on the same machine
> >(Athlon XP 2400+, 2 GHz, 1.5 GB RAM, VIA chipset, 2*Maxtor 120 GB
> >6Y060L0):
> >write read
> >2.4.20-ac1: 88,000 135,000 K/sec
> >2.4.21-pre7: 93,000 75,000
> >2.4.22-ac4: 94,000 82,000
> 
> Hi,
> 
>  I can attest a similar drop in read performance on a IA64 box going
> from a 2.4.19ish kernel to 2.4.22. In our setup the RAID0 is LVM, not
> MD.The RAID is used a a scratch device for a out-of-core finite element
> program (NASTRAN).
> 
>  The setup is some 20 disks on 4 controllers. "iozone" read/reread
> Performance went from about 400MB/sec to 260 MB/sec, while write went
> up a notch. Unfortunatelly the read performance is more important for
> the application in question.
> 
>  Due to the fact that I have no controll over the use of the system I
> cannot make any experiments to find out what killed performance. Sorry
> :-(
> 
> Martin
> 
> =====
> ------------------------------------------------------
> Martin Knoblauch
> email: knobi@knobisoft.de or knobi@rocketmail.com
> www:   http://www.knobisoft.de
> 
> 

And this isn't the read-ahead size change thing?