RE: Why optical disks are slow to seek etc...

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1 total messages Started by Jim Wiley Thu, 06 Nov 1986 07:58

#3118

Author: Jim Wiley
Date: Thu, 06 Nov 1986 07:58

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In article <2474@peora.UUCP>, joel@peora.UUCP (Joel Upchurch) writes:
> 	        ...WORM optical disk...
> 	                                         ...would not make good
> 	paging devices because of the awful seek times and rather anemic
> 	transfer rates associated with these devices. Has anyone seen
> 	any optical disks with numbers in these categories comparable
> 	to good magnetic disks?

Optical Storage International has a WORM optical disk with a transfer
rate of 262K bytes per second.  Thats about half as fast as a ST506
winchester.  The killer on the data rate is the 1.33M bits per
second SCSI interface.  I admit the seek time is poor, but SCSI
seems to me to be a pretty brain damaged way to sacrifice performance
for flexibility.  The data tracks on the disk spiral inward so that
once the proper track is found, any amount of data can be read or
written without 'changing' tracks.  At least it would be that way
if SCSI could keep up.  To stay on the same track requires the head
to jump back once every revolution.

Jim Wiley
DataSpan, Inc.

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