Ref: 02880004
Title: 3S/200 and 3S/400 Maximum Storage Capacity
Date: 06/22/88

Copyright 3Com Corporation, 1991.  All rights reserved.

On the 3S/200, the maximum disk storage we have tested is 1 GB (base unit
plus 3 x 300 MB expansion unit -- each unit with two 150 MB drives).
Using 106 MB drives, the most we have tested is 9 drives (one in the base
unit, 8 in expansion units).

We have tested the 3S/400 with 900 MB (a total of 6 drives, 150 MB each).


Controller limitations

The 3S/200 supports TWO drives per controller using the RLL controller
with the 106 MB drives.

Using the 150 MB drives with either the 3S/200 (in expansion units) or
the 3S/400, you can only use ONE drive per controller.  This controller
limitation may well change in the future, but there is no firm release
date yet.


SCSI requirements

You can have 7 devices on a SCSI bus.  The 3S/200 has tape and disk
drives on different buses, whereas the 3S/400 has only a single bus.
This theoretically means max of 6 drives on the 3S/400 (because one is
reserved for the tape) and 7 drives on the 3S/200 (with the tape on a
different bus).


Drive identifier limitations

There is a maximum of 24 drive identifiers available under 3+,
which limits the maximum number of permissible drives.  To increase
the amount of addressable disk storage space while staying within the
24-partition limit, increase the partition size by changing the cluster
size.


RAM requirements

A disk with a standard format of 512 bytes per sector and 4 sectors per
cluster requires ~1 KB of FAT per MB of disk storage.  Therefore, you
may have to add more RAM with a cache card if you want lots of expansion
drives.  For example:  with the 3S/200, you should add a cache card (3 MB
of RAM total) if you have >350 MB of disk storage.  This ensures that
there is enough RAM for FAT, data caching, and backup buffers.
