summary of: RAM disk driver for 4.2bsd/Ultrix

[Neville D. Newman]

A couple or three weeks ago, i posted an inquiry here as to the availability
of RAM disk drivers for 4BSD or Ultrix.  i did in fact receive such a driver
and it turns out that it was posted to net.sources a year and a half ago
(Nov. 84 if you want to check your archives).  However the person who sent
it to me made the same comment that i received from about 6 other people -
using extra RAM for disk buffers would be better (along with setting the
sticky bit on target files).

The rest of this posting refers to using the disk-buffer solution.

It was also suggested that /etc/update (performs regular sync()'s) be
changed to sync() less often than the norm, which is every 30 seconds.
i grabbed the source from our BSD machine and modified it to take an
optional overriding argument specifying the period in seconds.  You
don't really need the source, as it is a trivial program to reproduce.
Just set periodic alarms, and have the signal handler open important
system and local directories like /bin, /local, etc.

The way i found to change the size of the buffer space is to change the
initialization values of    nbuf  and   bufpages  in /vmunix  using
adb -w .  No one who responded mentioned how they did it, but without
source for this machine our choices are rather limited!  We have not
done this yet on anything more than an exploratory basis but based on
the report from the message file and the 4BSD source we casually
perused, we managed to probe both sides of the "point of diminishing
returns".  The first two changes gave very small increases because
we only changed bufpages;  the third time we overshot and the boot
configured with only 2Meg.

We'll get it yet.  Anyway, thanks to those who responded especially
John Gilmore.

					-neville
				Internet:  neville at umass.csnet