RE: Partitioning for Speed
On Tue, 1 Apr 2003, Joyce, Matthew wrote:
>
> I would have thought that for cached drives this becomes a moot point as
> such a high percentage of hits come from cache.
remember that most disks have 2MB of disk cache.. new drives are 8MB cache
drives spin at say 7200rpm
ie .138ms per revolution ( almost negligible compared to latency )
- we can move to a new track in say 100ms latency ...
- we can read 10 tracks in one second
you have typically 16 real heads ...
we typically have 64 sectors....
we typically have 512 bytes/sector
( 512 * 64 * 16 ) bytes per revolution --> 524KByte/revolution
- one revolution is .138ms
or about 5240KB/sec of disk reads ... ( say from ls -laR / )
- the 2MB disk cache will be flooded and not used at all...
- add 16 to 255 head mapping and that might slow down
some of the disk movement/reading but thats all in bios
and is still faster than mechanically moving the disk heads
or sum thing like that...
-- yeah... i've been looking to see how to make disks faster
and get the 100MB/sec disk transfers ... or even faster
c ya
alvin
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