High lngspins - IDS 9.30 UC2

[Andrew Hamm]

Art S. Kagel wrote:

>
> One thing we do to reduce/eliminate the possibility of the Clariion
> internal queues backing up is to maximize the number of spindles in
> use. IMM we configure 60 drives which as 5 RAID10 arrays of 5 pairs
> and 10 hot spares. Then we plaid the 5 stripe sets into one huge
> array bringing 50 spindles into any read request and 25 spindle pairs
> into any write request.

Woof! As long as the requests are 50x (or 25x?) stripe size. So your
readahead parameters are set to encourage transfers that large? What stripe
size do you use, btw? is it configurable on a Clariion?

[Art S. Kagel]

On Wed, 22 Oct 2003 20:02:57 -0400, Andrew Hamm wrote:

> Art S. Kagel wrote:

>>
>> One thing we do to reduce/eliminate the possibility of the Clariion internal
>> queues backing up is to maximize the number of spindles in use. IMM we
>> configure 60 drives which as 5 RAID10 arrays of 5 pairs and 10 hot spares.
>> Then we plaid the 5 stripe sets into one huge array bringing 50 spindles into
>> any read request and 25 spindle pairs into any write request.

>
> Woof! As long as the requests are 50x (or 25x?) stripe size. So your readahead
> parameters are set to encourage transfers that large? What stripe size do you
> use, btw? is it configurable on a Clariion?

Yes, each physical read is 25x stripe size. Stripe size is configurable as 2K,
4K, 8K, 16K, 32K, 64K, or 128K. Obviously we use a small stripe size and the
Clariion cache eats the balance of the physical read so read-ahead is not a
problem. Consequently we keep the ONCONFIG RA parameters very low: 8 & 2 or 16 &
2 typically. This prevents unneeded RA from IDS thrashing the cache which has
already been primed by the huge physical read. Needless to say when the EMC
maintenance guys forget to turn the cache back on after maintenance we notice
the difference!

Art S. Kagel