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

Isn't cache about saving frequently-used data? Writing
to cache is going to add cycles to the process, in order
to get benefit in other places (which I don't know about
yet).

I think there were results with various levels of cache
in the Performance Capabilities manual. Check'm out.
>
>
> -----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