RAM disk

[Steve Dyer]

In article <1010 at daisy.UUCP>, david at daisy.UUCP (David Schachter) writes:
> With the recent discussion of problems running 9600 bps without losing char-
> acters, someone bemoaned the inability to define in-memory filesystems.  Is
> there really no Unix driver to define in-memory simulated disk?  For some
> applications, such a facility would yield a substantial speed improvement
> without the need to alter the application for better memory buffering.

XENIX 2.2 and above has a RAM disk driver, although I have never bothered
to use it; at least on XENIX 386, it's far more effective to give all your
memory to the paging system.  I could imagine that certain specific applications
might benefit from using some of the memory as a RAM disk, and perhaps a XENIX
286 system with just plain too much memory, given a certain application
demand, could show a benefit.  The nice thing about XENIX is you can try it
with and without a RAM disk and make up your own mind.

Needless to say, none of this deserves to be mentioned in the same breath
as losing characters at 9600 baud.  Neither XENIX 286 or XENIX 386 loses
characters no matter how hard its disks are pushed.  I run 4 dumb serial
lines under XENIX 386, one at 9600, one at 19.2kb, and the other two at
2400 baud.  Even with all of them active, I've never had any problem.
If Microport drops characters, it's because of problems in their kernel
(undoubtedly too frequent or inappropriate spl() calls sprinkled throughout)
and not because the disk is getting banged on.  I'd pressure them to get
their drivers cleaned up; from what I've heard, it wouldn't surprise me if
a RAM disk driver from them would show the same problems!

-- 
Steve Dyer
dyer at harvard.harvard.edu
dyer at spdcc.COM aka {ihnp4,harvard,husc6,linus,ima,bbn,m2c}!spdcc!dyer