Excessive IO wait with megaraid card 2006-11-29 - By Jussi Silvennoinen
Back
> We have a (4) sun v40z's here to run some oracle databases. They have 6
> HD's in a hardware raid off of a LSI Logic MegaRAID 413Y (as cleaned
> from /proc/scsi/megaraid/1)
>
> Performance is fine doing it's main job (serving about 6 Lightly used
> Oracle databases).
>
> We are finding, however, that should you attempt to run a large tar job
> on the system, all four of the quad opteron processors end up stuck with
> 100% IO wait (when tarring say about a 4gb oracle database).
>
> We've tried using the megaraid2 driver which did improve things a bit,
> the system is a little more responsive during the tar, but not by much.
> Does anyone have any ideas?
>
> Either how we narrow down the problem/get more info, or (ideally ;)) a
> fix to our rather annoying problem? It seems to appear on all four
> boxses, using RHEL U7 (installed with U0, but up2dated), and using
> redhat-made drivers.
Do you have writeback-cache enabled on the logical drives? And do find out
which controller you have, 413Y is just the firmware version :)
LSI has software on their site to manage the controller from linux.
In my experience, there is something significantly wrong with Megaraid
when WB-cache is not enabled on the controller. I have numbers for
sequental writing on RHEL4, which uses a different driver though.
320-1 2-disk raid1
controller WB-off write 15mb/s
controller WB-on write 34mb/s
read 49mb/s
These numbers are simply 'time sh -c "dd if=/dev/zero of=foo bs=256k
count=32k ; sync" and count the transfer rate from that.
--
Jussi
--
Taroon-list mailing list
Taroon-list@(protected)
https://www.redhat.com/mailman/listinfo/taroon-list
|
|
