Very slow writes on RAID-5 using ciss driver on HP 1

[motoslide]

HP/Compaq Proliant ML350-G3 w/Smart Array 641 adapter.
SCO OpenServer 5.0.7 w/mp3 and "latest" (5.64a) ciss driver.
During heavy disk writes, the system pratically stalls for several seconds at a time. Reads are very quick.
System is configured with single-partition RAID-5.
I have two nearly identical new systems and both exhibit the symptoms.
Has anybody else had similar problems?
Any recommended fixes?
Are there newer drivers available?

 

[jfrantz]

Do you have the Battery Backed Write Cache module for this controller? I believe there are two models, 64MB and 128MB. If you are using an application which is disk I/O intensive, I would select the largest available. If not, you will need to get it, and you simply will not believe the difference in performance. Compaq (HP) disables the write caches on the physical disk drives to prevent data loss. It's annoying, but I have to say that I've never lost a bit of data when using a Compaq RAID controller.

Also, RAID 5 is much slower at writes than is RAID 1.

-Jeff

 

[motoslide]

Thank for the reply, JFrantz:
We don't have the Battery backed Write Cache, and so the Write Cache is disabled and cannot be Enabled. I'm getting nowhere fast with HP, so I think we may opt for a different controller.
Who's got a good recommendation for decent SCSI RAID adapter for OpenServer? HP/Compaq? Dell PERC? Something from AMI?
No guesses, please, only verified solutions.

Thanks!

 

[jfrantz]

I use Compaq Smart Array 5300 series controllers in my SCO servers. What kind of run-around are you getting from HP? When you're dealing with SCO, Compaq is a good solution with excellent support. I've dealt with Dell PERC controllers with SCO and don't care for their support.

You should be able to get the battery backed cache from CDW or similar. That way you'll just pop it onto the existing controller and you'll have great performance without having to do anything else and only a few minutes of down time. If you switch to a contoller other than Compaq you'll have to reinstall everything which may be a pain.

-Jeff

 

[stanhubble]

We sell the exact configuration. However we only use the raid controller for hardware mirroring. raid 5 is inherintly (sp?) slower. Depending on the application that is running there are some kernel parameters that can be tweaked to improve disk performance.

what does sar -d look like during the "heavy" disk times.

what i have found with the newer drives and machines that cutting down the kernel values of NAUTOUP to 1 and BDFLUSHR to 2 vastly increased our database applications performance.

 

[motoslide]

I gave up on RAID-5 and went to RAID-1, which only required the purchase of one additional drive. (Which was less expensive than trying the Memory Module for the 641 adapter).
Thanks, Stan for that information on NAUTOUP and BDFLUSHR. Setting those two values to "1" provided quite an improvement in my time tests.
After so many SCO installs all these years, it's great to know that there's still so much to learn.