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SubjectRe: RAID-0 read perf. decrease after 2.4.20
>Hello All!
>Has anyone else experienced a drastic drop in read performance on
>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
>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


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 Knoblauch
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