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RAID cache

Bernhard Mueller
Honored Contributor

RAID cache

Hi,

there is a SCSI RAID controller (A7143) in the machine which has the cache enabled (per sautil output) however, I wonder whether this is write-back or write-through?

looking at the saconfig man page there is no way of setting the cache to WBACK or WTRHU neither for a single LUN or all.

So I am afraid the controller is only capable of WTHRU. Is that correct?

Regards,
Bernhard
3 REPLIES
David Bell_1
Honored Contributor

Re: RAID cache

Bernhard,

I'm not sure if this will help you but here it is:

http://docs.hp.com/en/J6369-90001/ch02s01.html


http://docs.hp.com/en/J6369-90001/J6369-90001.pdf

This describes the caching process but doesn't specifically mention WBACK or WTHRU.

HTH,

Dave
Vincent Fleming
Honored Contributor

Re: RAID cache

The (several) docs I found indicate a write-back cache. Some said just "256MB write cache", others just said "256MB cache", but the thing that makes me think it's pre-set to write-back is that it's ECC protected, battery-backed memory. Battery-backed is for write-back cache only - there's no point in using a battery with write-thru or read caches...

good luck,

Vince
No matter where you go, there you are.
Bernhard Mueller
Honored Contributor

Re: RAID cache

Vince,

that is what I assumed, however, performance on non-striped (two disk RAID1) LUNs made me doubt it.

My hope was that someone with HP internal sources of knowledge might have been able to clarify this.

Happy New Year!

Regards,
Bernhard