EMC storage array tweaking

[Jeff Macfarland]

Peter Grandi wrote:
> Hi, I got to deal with several storage systems bought from Dell,
> which have a PE2850 with a FC host adapter attached to an EMC
> CX300 also bought from Dell.
> 
> Performance is not as good as it could be (that's an euphemism)
> and I strongly suspect that this is due to the cache on each
> CX300 disk being disabled.

You've got 1 GB of write cache on a cx300. Having cache on or off of the
physical disks themselves wont make anything faster except perhaps if
you're filling the cache and a forced flush is popping up. Check your
cache settings on the array to make sure write caching is on and you
have the upper and lower flush limits correctly.

> 
> On the PERCs there is something like '-EnDskCache' to turn the
> physical disk cache on or off, Is there some kind of way to
> enable it for CX300-attached disks?
> 
> Alternatively, I am considering attaching the CX300 disk array
> enclosures directly the the PE2850/2950s (bypassing the EMC/Dell
> provided Storage Processors). They seem to have fairly standard
> copper FC sockets and cables. What kind of host adapter can I
> use to do that?

Taking out the SPs seems like a bad idea. That's taking out all of the
benefits of an EMC array (or any storage array for that matter). AFAIK,
the backend loops are proprietary copper connectors.

-- 
Jeff Macfarland (jmacfarland at nexatech.com)
Nexa Technologies - 972.747.8879
Systems Administrator
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