Just a quick one... I'm running 2 adsm sites each has an IBM 3494ATL
     with just two 3590 drives (each atl). I would rest easier if I had 3
     in each ATL but the $46,000 price tag required me to cough up
     justification... I really couldn't...
     The two servers were built to cover each others load in the event of
     failure of one (machine, atl, communications, etc) so I have extra
     capacity in the disk pools and with the 10/30GB 3590J tapes in the atl
     WOW, talk about extra capacity...
     But those 3490E's are @ 2GB so you will be crunched a little there...
     When my second adsm environment was being built 3590's were in low
     supply and I had to rob one from the existing atl for the new ATL...
     we ran that way for @ 3-4 weeks... I never needed to but I always had
     the option to recycle with use of dasd... I was a little worried about
     the backed up recycles when we got the second drives. NO PROBLEM...
     recycles are real quick to give up the drives to other requests...
     Once when a client had bought a bunch of cheap 3rd party 9GB drives
     for their machine... they had 1 go bad, then the next day 2 more went
     bad... recycles were running but gave up the drives... I did see a
     little thrashing in that the client was restoring bits&pieces at a
     time so when he would pause for 10 or 15 minutes a recycle would start
     up, get some data moved then that client would stick in his next
     restore and the recycle would get bumped again...(client was restoring
     one db env at a time)
     anyway... with @80 clients containing 1+ terabyte of file systems I
     have no problem with only 2 drives  BUT  everything I'm running with
     is FAST & HIGH CAPACITY... fddi links to 95% of clients, 3590 tapes,
     and a couple drawers of SSA 4.5GB dasd for disk pools.
     We have already gone +50% origional guess-'da'-mation of covered nodes
     and are pulling in other servers (with independent backup solutions)
     so we can redeploy their equipment in other areas...
     This is business critical data so when I say no problems here... I
     mean NO PROBLEMS.
     gotta go,
     later
          Dwight



______________________________ Reply Separator _________________________________
Subject: Reccomended # of tape drives???
Author:  ADSM-L at unix,mime/dd.RFC-822=ADSM-L\@VM\.MARIST\.EDU
Date:    5/23/96 3:32 PM




     All,




          We are trying to gather some information on ADSM, and the
     hardware needed to support it. Our site (briefly) consists of UNIX,
     Novell, Windows/NT, and some OS/2. Total storage across all (30 or so)
     servers is approaching 160-170GB. We are looking at an RS/6000 F30
     with Fast Ethernet and about 12GB of disk reserved for ADSM storage
     pools to act as a dedicated ADSM server. Our tape subsystem will
     consist of _TWO_ StorageTek Timberline 3490E tape drives on an STK
     Wolfcreek silo (840 slots). Do you think two drives will be enough to
     handle the tape reclaim processing and still allow for restores during
     the day? Would you recommend three or more drives initially? Given the
     info above, can someone take a stab at approximating the time for tape
     reclaim processing? Any help would be greatly appreciated.

     Tom McKnerney