[net.unix-wizards] Is there a RAM disk for 4.2 BSD ???

russell@muddcs.UUCP (08/03/84)

[plplplplplplplplplplplplplplplplplplplplplplplplplplplplplplplplplplp]

	I was wondering if anyone has a RAM disk for 4.2 BSD running
on a VAX 750.  We have 5 Meg, so there is plenty to go around.  I'd
thought we could put /tmp on the RAM disk to save a little time (and
disk head wear) on compiles, etc.  Any experience with this sort of 
thing out there ??
-- 

		Russell Shilling
		{allegra,ihnp4,seismo}!scgvaxd!muddcs
		=====                           =====
	        
To: wade@nmtvax.UUCP
Subject: Re: AD&D PBM GAME: WE'RE STILL HERE, READ IF YOU STILL WANT TO PLAY.
In-reply-to: your article <433@nmtvax.UUCP>

[==================]

	Wade,
I'd like you to consider allowing me to play.

kermit@BRL-VGR.ARPA (08/10/84)

From:      Chuck Kennedy <kermit@BRL-VGR.ARPA>

We have two RAM disks on our 4.2BSD systems, one connected to a
VAX 780, the other connected to a VAX 750.  The RAM disks (which
we call Bulk MOS units) are DATARAM BS-202 units.  We originally
bought some of these units to help out our PDP-11/70 systems which
benefited greatly.  We've had pretty good luck with the units as
far as reliability, etc.

Now for the bad news.

The Bulk MOS units don't seem to be worth the effort for large virtual
memory machines.  They are not cost-effective when considered against the
choice of buying another dedicated disk for /tmp space.  There is some
performance improvement from using the Bulk MOS since there is no rotational
latency and no seek penalty.  However, for the cost of a Bulk MOS unit, you
can easily buy a dedicated Eagle drive and it's own controller.  I certainly
would not worry about disk head wear.
	Good luck,
	 -Chuck Kennedy

mike@BRL-TGR.ARPA (08/16/84)

From:      Mike Muuss <mike@BRL-TGR.ARPA>

BRL has 2 VAX systems with RAM disks, on is a 780, the other a 750,
both running 4.2 BSD.  We use the Dataram BULK MOS product,
which emulates an RF-11 head-per-track disk;  we did the driver
ourselves (it's availible).

Advantages:  No head motion for /tmp

Disadvantages:  The UNIBUS is busy enough without this stuff too.
Transfer rates are generally less than what a MASSBUS device could do.
Given the cost of the bulk mos device, you are better off buying
more moving head disk drives and putting /tmp & some archival stuff
out there (assuming you add MASSBUS disks).

Best,
 -Mike Muuss

(301)-278-6678
  AV  283-6678
  FTS 939-6678

ArpaNet:  Mike @ BRL
UUCP:     ...!{decvax,cbosgd}!brl-bmd!mike
Postal:
  Mike Muuss
  Leader, Advanced Computer Systems Team
  Computer Techniques and Analysis Branch
  Systems Engineering and Concepts Analysis Division
  U.S. Army Ballistic Research Laboratory
  Attn: DRXBR-SECAD (Muuss)
  APG, MD  21005