Hard Disks for AT

[M.R.Murphy]

In article <1181 at umbc3.UMD.EDU> brian at umbc3.UMD.EDU (Brian Cuthie) writes:
)In article <409 at ucrmath.UUCP> jantypas at Soft21.Riverside.CA.US (John Antypas) writes:
)>Hello out there!
)>
)>Can someone out there help me?  I am running Microport Unix Sys V/AT
)>[deleted]
)>What types of drives can an AT use? (Standard MFM Western Digital controller)
)>[deleted]
)>Many thanks.
)>
)>John Antypas -- Soft21 --21st Century Software:
)
)Well, stay away from the Seagate drives.  They are pure crap.  They quote
)their access times a little funny.  Like claiming that their average seek
)time is 28 ms on the 4096 when the track to track time is 8 or 9 ms !  Any
)good drive will have a voice coil actuator that can deliver a track to track
)time below 6 ms. 
)	
)There are several manufacturers who make good, fast, drives.  These include
)MAXTOR, CDC, PRIAM and some more that escape my memory now.  It is very 
)important not to underestimate the amount of time spent waiting for a slow
)disk drive.  There is no point in running UNIX on a fast processor just to
)slow it down with a piggy drive.
)
)Hope this helps...
)
)-brian

We use ST4096 drives with WD controllers on uPORT SVAT and don't find
the systems "piggy". Also ST251-1 drives. Prices are reasonable.
Unix(tm) file system caching helps.

  "... In our own system, for example, we have user files on an RP,
   the root on an RF fixed-head disk, and swap on an RK. This is
   best for us since the RK has a faster transfer rate than the
   rather slow RF, and in swapping the transfer rate rather than access
   time is the dominant influence on throughput."
                             SETTING UP UNIX -- Sixth Edition

Transfer rate is still important. The effects of small memories coupled
with slow disks are easy to observe, not so easy to measure. It really
seems to help when SVAT has 1100K of buffers rather than 100K of buffers.
It also seems to help when the disk is 28ms rather than 70ms :-)
-- Mike
Mike Murphy  Sceard Systems, Inc.  544 South Pacific St.  San Marcos, CA  92069
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