On Wednesday, November 05, 1997 11:04 AM, Bill Lancaster
[SMTP:[log in to unmask]] wrote [in part]:

> At 09:29 AM 11/5/97 -0800, Guy Smith wrote:
> >2) Many arrays come with significant RAM caches and can reduce I/O time
by
> >avoiding disk reads/writes.  Large caches can be found on single drives,
> >but it is fairly rare.
>
> Array cache is generally ineffective on MPE/iX.  This is mainly because
MPE/iX
> does such a great job prefetching.  This is particularly true of EMC
cache.
>  It
> is usually much, much better to drop cache from disk subsystems and
increase
> memory on the 3000.

True enough, though for systems with high volume, but extremely random I/O,
disk caching can boost performance.  Also, cache on arrays comes into play
for write operations, especially operations which cause locks until the
write is completed.  Of course, this is so application specific that how
much disc based write cache helps any given system is difficult to predict.