You are correct Sir !

     I would like to say it was a poor choice of words but I think its more
     along the lines of being brain dead ;-)

     What I was refering to was that...
        All the SSA adapters driving the  DB & LOG volumes were on buss 0
        All the SSA adapters for the DBCOPY & LOGCOPY vols were on buss 1
     The way I had the files placed on the dasd, the first disk out a loop
     port would be either a DB, LOG, DBCPY, or LOGCPY.  By keeping all the
     primary files on buss 0 only the primary writes hit buss 0, by keeping
     all the copy files on buss 1 only the copy writes hit buss 1. IF (I
     think) I had split the (redundant, "higher availability") ssa controll
     cards across the busses then each write pairs (primary & copy) might
     or might not go to the same buss.

     A better description would be sometimes both the pairs of writes could
      hit the same buss, other times they would still hit each buss and in
     the event of a single ssa card loss (say a copy vol controller) the
     primary writes would still float between busses (going to the card
     with the shortest path to the disk) but all the copy writes would now
     be locked into going through the buss with the still functioning ssa
     card for the copy vols resulting in an uneven distribution.

     later,
           Dwight


______________________________ Reply Separator _________________________________
Subject: Re: ADSM and SAN
Author:  psz1 (psz1 AT cornell DOT edu) at unix,mime
Date:    2/3/99 3:11 PM


Hey Dwight,

>            I could have split the redundant ssa cards across the
>     internal busses but that would have doubled the data across each buss
>     during normal operation and only paid off if an internal buss failed
>     and the processor stayed running...

I didn't realize this would double the bus load!  We have our server
configured with 2 adapters, one on each bus.  Are you sure about this?
Does 1 I/O op somehow drive both SSA adapters if they are on the same bus?

>     When their Seascape goes into full swing... you will be able to move
>     all your existing SSA disks into the Seascape environment !  So if you
>     have a bunch of older 4.5 GB ssa drives that you have replaced with
>     the 9.1 GB's... don't throw the 4.5's away just yet... well, if you
>     must  you may trash them my way ;-)

True.  Hey, have you looked at the new D40 drawers yet?  I just ordered
one, but haven't gotten it yet.  I understand that there's a new format SSA
drive for the new drawers, so you can't move drives between mod 10/20
drawers and D/T40 drawers.  Bummer.  I believe the new drawers will support
the higher speed adapters when they come out later this year.

Regards,
..Paul


--
Paul Zarnowski                         Ph: 607-255-4757
Paul Zarnowski                         Ph: 607-255-4757
747 Rhodes Hall, Cornell University    Fx: 607-255-8521
Ithaca, NY 14853-3801                  Em: psz1 AT cornell DOT edu