Smart Array 3200

[Dave Orton]

Can anybody help with these questions regarding the cache functionality on the 3200 controller or point to Whitepapers concerning this matters.
(1) We are running MS Sql Server and its important that the transaction log is written to disk before continuing. Setting the write cache down to 0% - does this effectively disable the write cache?
(2) Can write cache be selective on a specific array?
(3) I understand that the SCSI drives have onboard cache - how can this be disabled to prevent a similar occurrence to point(1).
(4) Would upgrading the controller give more control over fine tuning these parameters.

Thanks

[Janine Bertolo]

Hi Dave;

1) setting the write cache down to 0% does effectively disable the write cache on your controller; you can also disable the cache at the logical drive level using the Array Configuration Utility - this would disable both read and write caching ability

2) the % read/write is set at the controller level and takes precedence, so you cannot control it for each array on the controller; you can set your % read/write at the controller level and then disable cache to one logical drive on the array

3) this is not an issue at the hardware level; you can make adjustment settings within win2k (basically the OS recognizes a cache on the logical drive, not the physical hard drives); consult your Microsoft references on this.

4) No; all of our cached - array controllers function in the same way.

We publish an SQL sizer that you may find helpful. You can download it with pdf instructions at http://activeanswers.compaq.com/ActiveAnswers/Render/1,1027,554-6-100-225-1,00.htm

Cheers,

Janine

[Dave Orton]

Hi Janine
Thanks for your detailed reply.
Since posting my question, I have continued to search for answers and found the Smart Array 3200 Ref Guide.
Concerning the disabling of write cache on SCSI drives it mentions the 'Advanced Features' menu in which setting to 'disable' will turn off write caching on the physical SCSI drives. This seems what I'm looking for - is it? (can you confirm).

I know I'm changing the subject slightly but I'm looking towards putting on big IDE drive in a ML570 say 160mb or more (for Sql backups/Ghost Images etc). Any opinions or words of wisdom? If you think this is just a plain crazy idea, then I shall not be offended if you tell me so!

(1) Can I use the 2nd 'low profile' IDE channel?

(2) What cables would I need?

(3) Could I boot from such an IDE device?

Thanks again

Dave Orton

[Jez Thomas]

I'm a bit puzzled by what you mean here. IIRC, a 3200 has a battery-backed up cache. Therefore, if you have a catastrophic power loss to the server, anything not written by the cache is just held, and will be written to the cache when you power back on.

Also, as the array card handles all disk transactions, we shouldn't need to care where the data is phisically, as long as it's available logically.

Now I know I'm answering the question I think you should be asking here, and I'm doing so without the support of documentation, but if I have missed something, I'd be keen to know.

Can you explain why it should be so important for the log to be physically on the disk rather that just logically?

Rgds, Jez.

[Janine Bertolo]

Hi Dave;

My apologies at taking so long to get back to you - I was on vacation.

Yes, turning off the write cache is the feature you're looking for.

As far as IDE hard drive support off the embedded controller on a ProLiant, it simply won't work. The controller itself is meant only for cd-rom support and can't provide the burst transfer newer bigger hard drives require.

Hope that helps,

Janine