🚀 go-pugleaf

kallisti (adal@urquell.disy.cse.unsw.EDU.AU) wrote:
: I heard through James Lockwood's pineal gland that:
: >This is actually less important than you might think with only the system
: >drive installed.  The drive that can sustain more than 10MB/s is still
: >relatively uncommon, the benefits of faster SCSI busses are mainly realized
: >when multiple drives are attached.
: 
: Most drives after a certain vintage can do above 10mb/sec sustained;
: any drive one buys nowadays which is SCSI and 7200rpm will easily do

I do agree with this, but I suspect that most people who are relying on
Ultra 1's are not ready to pour large amounts of money into brand new SCSI
disks.  The internal drives that most of these systems shipped with are
capable of 10MB/sec only under ideal circumstances.

I personally deem the slower network performance of the Ultra 1 to be a
more important factor in deciding which machine to purchase.

: 15.  The other half of the issue is that a slow bus will destroy a
: large part of the advantage of the diskcache, because you're reading
: data into the cache faster than it can empty onto the CPU.

This is nearly a complete nonissue due to the way that Solaris handles
disk caches.  The write cache will not be useful during normal operation
as the system must ensure that all data is committed to physical storage
before it reports an I/O request as completed.  A read cache is not very
useful as main system memory does a better job of it.  Burst write
performance is still limited by physical disk speed.

The key benefit of drive caches at this point is the coalescing and
reordering of I/O requests and read-ahead.  This is not hampered unduly
by a slower bus speed.

It would be very interesting to see high performance drives start coming
with a few megabytes of NVRAM for cache.  The cost would be relatively
low and the gain in write performance high.

-James