Re: Disk issue: More arms versus improved hardware

[Larry Bolhuis <lbolhuis@xxxxxxxxxx>]

Rob,

  Certainly you are correct. In theory if one drive could be made fast
enough to handle the IO for a system then that's all it takes. The 10K
8G units combined with the IOPs and IOAs of today's 270/8xx series will
perform roughly 70% better than 4G drives with older controller
technology. In other words 3 of these would perform about the same as 5
4G units. (Move the same amount of data at the same utilization rate).

  Without doubt the controllers will continue to get faster, bigger
caches, and smarter code. Drives too will continue to get faster, but
there is a limit with all things physical.  RPM will likely still climb
some because platters continue to get smaller, this of course reduces
latency.  Seek times are in a catch-22. If you want to seek faster you
must push the heads harder to get them there quicker, but you must then
strengthen the arms holding the heads to sustain the additional push,
which usually makes them heavier, which means you have to push them
harder....  Some guy named Newton comes to mind here.  Improved
materials can help, but before we see any big improvements here I'd
expect some new technology will need to be released.

  - Larry

> I've heard this argument that more arms is better quite often.  But
> sometimes I wonder if it is true versus improved performance of the newer
> hardware.  For example, let's say you could get IBM PC original 10MB hard
> drives into a single level storage machine like the AS/400.  How many of
> them would it take to give you the performance of the 8gb drive?  Or could
> it ever be done?
> 
> I will admit the 17gb drive is better left for non performance critical
> applications.  We use them on a secondary ASP for backing up our PC's using
> ADSM.
> 
> Rob Berendt

-- 
Larry Bolhuis           | Cogito Ergo Vendo iSeries 
Arbor Solutions, Inc.   |
(616) 451-2500          |               (I think, therefore I buy iSeries.)
(616) 451-2571 -fax     |
lbolhuis@arbsol.com     |        #3  1951-2001
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