Most of these discussions about EIDE vs. SCSI and transfer rate are moot,
since the highest performing drives available today (like a Seagate Cheetah
10K RPM drive) have only a maximum formatted internal transfer rate of
28Mbytes/sec. Far short of the interface maximum. These high end drives
are not available in EIDE, they are available in SCSI or FC only. The internal
formatted transfer rate is the rate the formatted data comes off the platters.
This is bound by the physical properties of the drive including sector density
and rotation speed.

This disparity has always occurred. Never have I been aware of any disk where
the formatted internal rate comes anywhere close to the maximum speed of the
interface. As disk technology improves (density), so do interfaces. Even when
reading strictly off the on-disk cache, it means nothing. The cache is usually
1Mbyte, so at 80Mbytes/sec, the cache is exhausted in a fraction of a second.

Yes, SCSI tpyically carries a price premium, both in the controller and the
drive, but you usually have more life in the controller. My 2940U controller
is just now becoming the main limitation, and I have had it for years. Also,
you do get more with a decent SCSI subsystem, besides the drive itself being
of higher performance, SCSI gives you benefits like multi-threading of I/O
requests, disconnect/reconnect, and scatter/gather.

For the typical consumer system, the benefits of SCSI are hard to justify,
so EIDE is the best choice. For harder working systems, SCSI is usually a
better choice.

BTW, you can get 50Gb disks now (SCSI or FC only).

Russ Poffenberger               Engineering Specialist
Schlumberger Technologies ATE   DOMAIN: [log in to unmask]
1601 Technology Drive
San Jose, Ca. 95110             Voice: (408)437-5254  FAX: (408)437-5246

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