EVA8400 and fine tuning of Cache Policies

[charlie_bulosan]

Hi All,

Has anyone fine tuned their EVA cache policies? Any performance benefits?

We have an EVA8400 with 22GB cache but still we utilize the default Cache Policies for the luns, i.e.
Read Cache: On
Mirror Cache: Mirrored
Write Cache: Requested:Write-Back
Actual: Write-Back

Could anyone explain the benefit of the default cache policies?

Are these policies good for a big cache EVA like the EVA8400?

Many thanks again for your help.


Kind Regards,
Charlie

[susanta_dutta · Accepted solution]

Hello Charlie,

Yes, default cache policies are the best for better performance and redundancy. Here are the explanations of these settings:

read caching
A cache method used to decrease subsystem response times to a read
request by allowing the controller to satisfy the request from the cache
memory rather than from the disk drives. Reading data from cache memory is
faster than reading data from a disk. The read cache is specified as either On
or Off for each virtual disk. The default state is on.

write back caching
A controller process that notifies the host that the write operation is complete
when the data is written to the cache. This occurs before transferring the
data to the disk. Write back caching improves response time since the write
operation completes as soon as the data reaches the cache. As soon as
possible after caching the data, the controller then writes the data to the
disk drives.

mirrored caching
A process in which half of each controllerâ s write cache mirrors the companion
controllerâ s write cache. The total memory available for cached write data is
reduced by half, but the level of protection is greater.

Regards
Susanta

[charlie_bulosan]

Hi Susanta,

Our HP storage specialist also has confirmed the same thing that the default cache policy is better for us, and generally for most requierements.


Many Thanks.
Charlie