Very Computer

I'm facing performance problems with Mylex (DAC960) controller, using
the latest update kernel 2.4.18-24.7.xsmp, tried a single CPU box
but the same problem.

Copying with dd from one disk to another a big file (390 MB) shows:

dd if=/dev/rd/c0d1p2 of=test.file bs=40960 count=10000

1. Speed up to >150 Mbyte/sec for perhaps 1 sec.
2. Speed drops down to 0 Mbyte/sec for a few seconds
3. Back to 1.

This happens a few times until the file is created, overall performance
is about 6-8 MByte/sec.;(

Pretty poor thinking about the 15K rpm SCSI disks in the box. It doesn't
matter if it's RAID1 or RAID5. The same test on another system with the
same Mylex shows the same poor performance.

The same test on another system with AMI Megaraid controller shows a
constant speed of >20MBytes/sec (RAID1), 16-32 MBytes/sec overall.

Anyone an idea?

Enabled write cache on the controller, but it didn't helped.

--
Michael Heiming

Remove +SIGNS and www. if you expect an answer, sorry for
inconvenience, but I get tons of SPAM

[DAC960]

Quote:>This happens a few times until the file is created, overall performance
>is about 6-8 MByte/sec.;(

That's probably as fast as it can. I observed the same behaviour
on a RAID5 system under WinNT, using the Mylex-provided driver.
OTOH, this is a nowadays obsolete ISA card, and the bottleneck
may well be the bus and not the controller.

Michael

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Michael Heiming

Remove +SIGNS and www. if you expect an answer, sorry for
inconvenience, but I get tons of SPAM

[...]

Quote:>> OTOH, this is a nowadays obsolete ISA card, and the bottleneck
>> may well be the bus and not the controller.
>Nope, this is a 64bit PCI Ultra 160 SCSI RAID controller.

Michael
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          Lumber Cartel Unit #456 (TINLC) & Official Netscum
    Note: If you want me to send you email, don't munge your address.