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From: Don Bowman <don@sandvine.com>
To: 'Jens Schweikhardt' <schweikh@schweikhardt.net>,
	Scott Long <scottl@freebsd.org>
Date: Wed, 12 May 2004 14:37:31 -0400
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cc: freebsd-scsi@freebsd.org
Subject: RE: 2120S Stripe - abysmal performance
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From: Jens Schweikhardt [mailto:schweikh@schweikhardt.net]
> 
> On Wed, May 12, 2004 at 11:48:06AM -0600, Scott Long wrote:
> ...
> # I can't remember how the 2100 BIOS works, I'll have to take a look.
> # I thought that it was an attribute that was set when the array is
> # created.
> 
> Yes, and once its set at array creation time it apparently can not be
> changed. I deleted the array and created it anew to disable read
> caching. This did not yield any perfomance gain by itself. After I
> changed the cables I now have 79MB/s (formerly only 29MB/s, a single
> disk has a sustained read speed of 71MB/s at the outer sectors). Next
> thing will be going back from forced U160 mode to U320. I'll 
> report the
> results, so watch this space :-)
> 

With aaccli, one can see the values of the cache:
AAC0> container show cache 0
Executing: container show cache 0

Global Container Read Cache Size  : 0
Global Container Write Cache Size : 16203776

Read Cache Setting        : DISABLE
Write Cache Setting       : ENABLE ALWAYS
Write Cache Status        : Active, not protected, battery not present

and set it:

AAC0> ? container set cache
Executing: container set cache help
container set cache - Sets caching parameters for a container.  Useful only
if
                      a native operating system's file system resides on the
                      container.
  FORMAT - container set cache {container}
    /read_cache_enable - If you set this switch to TRUE, the command enables
                         the read cache for the specified container.
    /unprotected - Specifies whether to set the container's write cache to
                   disable, enable when protected, or enable always. You use
                   this switch in conjunction with the /unprotected switch
to
                   accomplish the desired setting. See the CLI Reference
                   Guide for more information.
    /write_cache_enable - Specifies whether to set the container's write
cache
                          to disable, enable when protected, or enable
                          always. You use this switch in conjunction with
the
                          /unprotected switch to accomplish the desired
                          setting. See the CLI Reference Guide for more
                          information.