Adding a disk - which one?

[hurf at batcomputer.UUCP]

	We have a uVaxII with ba123 box, 3 rd53 disks on rqdx3, Ultrix32m 1.2
   and we are shopping for a big disk. The Systems Industries track record
   around here is very, very good so we are leaning towards one of their 
   configurations. Our choices are dictated somewhat by budget so we have 
   focused in on the 340 MB qda51 with the 9751 disk & the 497 MB qda98 with
   the 9798 disk. The major differences are the seek time & transfer rate
   with the smaller disc being 18ms & 1.9mb/s and the larger 30ms & 1.2mb/s.
   For comparison the rd53 is 38ms & .6mb/s & the RA81 is 28ms & 2.2mb/s
   DEC will not sell the RA81 for connection to the ba123 box & is pushing 
   instead the rd54 150mb disk which uses the rqdx3. It is not a cost
   effective alternative for us.

     We have a multi user system still growing but the major usage is some
   application numerical codes, TeX, related emacs & vi sessions, some program
   development and fairly heavy network traffic like rlogin, telnet & tn3270.
   My question then is whether the uVax bus can take advantage of the faster
   transfer rate & whether or not the difference in xfer rate will, in the 
   long haul, become a bottleneck. Also whether the performance gain in seek
   time will amount to much as the system becomes more loaded.- Will more
   memory have a tendency to offset this?

    Are there other alternatives we should look at? - the local emulex dealer
   will sell me a board for the fujitsu but I have to get my own disk, etc
   and it doesn't look like it is worth the hassle.

    What would you do?
    What have you done?
 
              thanks in advance,
				Hurf
						reply to me & I will summarize
     Hurf Sheldon			Arpa.css: hurf at ionvax.tn.cornell.edu
     Lab of Plasma Studies	
     369 Upson Hall			phone: 607 255 7267
     Cornell University
     Ithaca, N.Y. 14853