RE: disk cache battery story

Well everybody's entitled to an opinion <grin>

But consider that the first disk drive was 5MB spinning at 1200 RPM.

Now you've got 400GB at 7200 RPM or 140GB at 15000 RPM.  An increase at
most 80,000x in capacity and 12.5x in speed.

Capacity's gone up considerably, but speed hasn't and speed as we know
is the big key in performance.

CPU's on the other hand, have gone from a few MHz to a few GHz, a 1000x
increase.

If disks had kept up, we'd be running 1,200,000 RPM disks or something
that could provide an equivalent performance.

The same physics applies to the addition of CPU caches.  The memory and
busses in the systems haven't been able to keep up with CPU speeds.

Charles Wilt
--
iSeries Systems Administrator / Developer
Mitsubishi Electric Automotive America
ph: 513-573-4343
fax: 513-398-1121
  

> -----Original Message-----
> From: midrange-l-bounces@xxxxxxxxxxxx 
> [mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Doug Hart
> Sent: Tuesday, February 28, 2006 6:40 PM
> To: 'Midrange Systems Technical Discussion'
> Subject: RE: disk cache battery story
> 
>  
> I can't agree, disk technology has done very well in the last 
> few years.
> Now we have 15,000 rpm Ultra SCSI disks 140Gig in size.  This 
> is a long ways
> from what we had 5 years ago.
> Our processors now have huge L2 and L3 caches.
> 
> 
> 
> --
> Doug Hart
>  
>  
> 
> -----Original Message-----
> From: midrange-l-bounces@xxxxxxxxxxxx
> [mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Wilt, Charles
> Sent: Tuesday, February 28, 2006 6:21 PM
> To: Midrange Systems Technical Discussion
> Subject: RE: disk cache battery story
> 
> I don't know the specific answer....
> 
> But consider the rate of improvement of disk vs. the rate of 
> improvement in
> CPU's.
> 
> Disks just haven't kept up, thus the need to add caching.
> 
> HTH,
> 
> Charles Wilt
> 
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