topic Re: VA7400: enable read cache using armmgr in Disk Enclosures

VA7400: enable read cache using armmgr

William Wan_1 — Tue, 30 Nov 2004 11:49:35 GMT

VA7400 with firmware HP19
attached with 4 N-class 11.0 through 2 brocade switches.

A armdsp -a is attached

Hi,

It's known that the default configuration for a VA7400 disable the read cache.

I want to enable read cache and I want to know if this can be done online and if there is any consequences.

After reading man for armmgr, I still don't know if this can be done online. Does anyone has experience with this option??

-P Enable read ahead operation of LUNs being accessed.
-r Change the apparent state of read cache disabled

Which one should I use?

Regards,

William

Re: VA7400: enable read cache using armmgr

Roger Buckthal_2 — Wed, 01 Dec 2004 12:30:14 GMT

Read cache is enable by default. Look in armdsp:

Read Cache Disable:___________________False

Yeah, backward logic, but too negitives make a positive!

Re: VA7400: enable read cache using armmgr

William Wan_1 — Thu, 02 Dec 2004 19:31:11 GMT

Can anyone else comfirm this?
it sounds so unusal.

from armdsp:
Read Cache Disable:_______False
Write Cache Enable:_______True

Does it mean that both read and write cache are enable?

Is there otherway to determinate these? or test this?

I was doing some read/write test on this VA earlier in all kind of set up.

In any cases, write I/O is like 3 times higher / faster then read I/O

????? can anyone explain this??

regards,

William