BI & CI in Ultrix land

[Alan's Home for Wayward Notes File.]

In article <7373 at cbmvax.UUCP>, grr at cbmvax.UUCP (George Robbins) writes:
> Well, as a capacity planning excercise, I'm looking at either a 6X00
> or one of these newfangled 58XX systems and trying to come up with
> a realistic configuration.
> 
> A few questions:
> 
> 1) Are there any real problems with the BI serial controllers, either
>    the DMB32 or DHB32?  For example two of the current unibus controllers
>    are seriously compromised: the DMF32 has hard-wired modem control that
>    makes it all but useless with smart modems, and the DHU11 output speed
>    is really limited to 9600 baud, with obvious consequences.

	Even though I have a DMB32, I've never had the oppurtunity
	to make much use of it.  I've heard (but never verified)
	that it will run at 19.2 Kb.
> 
> 2) Are there thruput/performance limitations that would favor multiple
>    DMB32's vs a DHB32 or the opposite?  How large are the input fifos
>    and are they shared between all lines? 

	See above.

> 
> 3) Is anybody out there using CI attached disks on an Ultrix system?
>    How does performance compare to Massbuss or BI attached drives?

	I have 20 disks on the 8800 that I'm the system manager of.
	12 are on an HSC70 and others spread across two KDB50's,
	mostly because I didn't have enough requestors in the HSC.
	For typical I/O usage, I'd say the performance is about
	same.  If you start doing lots of sequential I/O at the
	same time, multiple KDB50's have an advantage because you
	can easily saturate the CI adapter.  

>    Does Ultrix really get any benefit from the rather expensive CI
>    hardware? 

	I believe it does.  If you have multiple systems you can use 
	the CI as a network interface and share disks more easily.  As 
	for cost, I calculated the cost per port once and did find the 
	HSC/CI more expensive (for 32 ports) than the KDB50's.  I'm not
	sure if took into account the extra expansion cabinets needed 
	for the additional KDB50's.

> 
> 4) How about CI attached tape drives?  The lack of direct attachment
>    for TU78 class drives is a real bummer.  I don't particularly want
>    to downgrade to a TU81+.  Does anyone actually use TK70's for
>    backup on mid-range systems?

	Being able to share our TA78's with the VMS cluster was
	my biggest reason for getting an HSC and CI adapters.  I've
	only played with a TK70 on a VS3500, so I can't comment much
	about it.  I don't see any reason that a VAX 6000-xxx or
	DECsystem 5800 shouldn't be able to keep it streaming, so
	it will be close the same speed as a TA78/9.  I won't know
	what the affective capacity is, but I'd guess it to be between
	250 MB and 295 MB.  The cartridges are more expensive then
	a 9-track tape, so the cost per MB is probably higher.  They
	do have advantage of being smaller if MB per square foot is
	a concern.
	
> -- 
> George Robbins - now working for,	uucp: {uunet|pyramid|rutgers}!cbmvax!grr
> but no way officially representing	arpa: cbmvax!grr at uunet.uu.net
> Commodore, Engineering Department	fone: 215-431-9255 (only by moonlite)

	Alan Rollow, Digital Equipment Corp.
	Database Systems, Colorado Springs CO.