RE: disk arms (was RE: Tips for user ASP)

["Steve Richter" <srichter@xxxxxxxxxxxxx>]

-----Original Message-----
From: midrange-l-admin@midrange.com
[mailto:midrange-l-admin@midrange.com]On Behalf Of Vernon Hamberg

>If RAID protection is used in the same environment, the DASD arms become
>the bottleneck. If protection is required, using mirrored arms for the
>journal receiver DASD will provide significantly better performance than
>RAID protection. However, unprotected DASD arms will allow the highest
>overall transfer rates and best overall performance when using Opticonnect
>for remote journal.

Doesn't the presence of a disk cache, esp a large cache, invalidate all
these considerations of arms and raid protection ?  A cache is non-volatile
memory. When writing to a cached mirrored pair I assume the system is
writing to paired cache. So, unless the cache is full, there will be no
delay in performing the mirrored write.

Steve Richter