RE: High CPU usage (up to server hang) under heavy I/O load

[Tom Sightler <ttsig@tuxyturvy.com>]

On Fri, 2004-08-13 at 11:46, Sylvain COUTANT wrote:
> Hello Matt,
> 
> > Which server please?
> 
> PE 2600 manufactured in June with latest PC BIOS and SCSI (PERC4/DI)
> BIOS/Firmware. We also tried downgrading to the previous release (as we have
> another PE2600 which runs fine with them) but it didn't do.

What driver are you using for the PERC?  We have a Dell 1750 with a
PERC/4Di which uses the megaraid driver under RHEL 3 and it has this
same problem, but only when writing to drives connected to PERC
controller.  The system also has a Qlogic 2312 card connected to a EMC
CX400 storage controller and performance to this device is fine, even if
I setup and LUN on a single ATA disk.

During heavy writes to the drives attached to the PERC4/Di the system
becomes practically unusable.  I've been wanting to try the 'megaraid2'
driver to see if this gets rid of the issue but I haven't been able to
try that yet.

We have some older systems with PERC2/DC cards which also use the
'megaraid' driver but they don't seem to experience this issue so I'm a
little suspicious that perhaps this driver simply doesn't work that well
with the newer megaraid-like controllers.

Later,
Tom