[comp.os.vms] Ra82 vs sa482

XRBEO@VPFVM.BITNET (Bruce O'Neel) (01/28/88)

Have a question regarding ra82s vs a SA482.  We've been told that on a
BI bus machine (8250), we can use two KDB50 disk controllers to connect
the machine to either 4 RA82s or 1 SA482.  The result of using a two
KDB50s is that we would get higher i/o through put because
the two KDB50s would work in parallel.
  Is this true?  Thanks in advance for you answers...

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XRBEO@VPFVM.BITNET (Bruce O'Neel) (01/28/88)

----------------------------Original message----------------------------
Have a question regarding ra82s vs a SA482.  We've been told that on a
BI bus machine (8250), we can use two KDB50 disk controllers to connect
the machine to either 4 RA82s or 1 SA482.  The result of using a two
KDB50s is that we would get higher i/o through put because
the two KDB50s would work in parallel.
  Is this true?  Thanks in advance for you answers...

-------

thierbac@umbc3.UMD.EDU (Ed Thierbach ) (02/09/88)

In article <8802060354.AA02754@ucbvax.Berkeley.EDU> XRBEO@VPFVM.BITNET (Bruce O'Neel) writes:
>Have a question regarding ra82s vs a SA482.  We've been told that on a
>BI bus machine (8250), we can use two KDB50 disk controllers to connect
>the machine to either 4 RA82s or 1 SA482. 

Actually, 1 SA482 is 4 RA82s in one (big) box.  As far as I know, each drive
is cabled separately, just like the RA81 'four-pack' you can get.  (We're
currently evaluating them against the SI93C drives from System Industries).

> The result of using a two
>KDB50s is that we would get higher i/o through put because
>the two KDB50s would work in parallel.
>  Is this true?  Thanks in advance for you answers...

What you would do is hook up 2 drives to 1 controller and the other 2 drives
to the other controller.  (At least I don't *think* you can dual-port disks
between KDB50s, the way you can with HSCs.)

Since one controller can transfer data from only 1 drive at a time, this allows
2 simultaneous data transfers.  The trick is to spread your I/O load evenly
across the 2 controllers.  For example, you may want to put your secondary
page and swap files on the controller that *doesn't* have your system disk
on it.  You also probably wouldn't put two high-throughput databases on the
same controller (much less tht same disk).

Hope thi helps!

---
Ed Thierbach
VAX System Manager
Roy F. Weston, Inc.

(yes, formerly of the University of Maryland, University College)