Date   : Wed, 08 Jun 1983 05:49:00 EDT
From   : Roger L. Long <BYTE@mit-mc>
Subject: Re: RAM disks with UNIX

Yes, I believe it would be possible to write a RAM disk driver for
UNIX, but I think that if you are going to put a substantial
amount of memory into a system for such a purpose, it could be better
utilized by other means.

For instance, certain mods have been made to various UNIX systems to
leave sharable code in memory once you are finished using it until
such time as you want to use the code again, or you need the memory
for something else.  Having a large amount of main memory would
mean less chance of such things having to be loaded from disk again,
so in a sense, you are obtaining the same benifits of having a RAM
disk by other means.

Also, UNIX manages a large buffer pool, and reuses its buffers with
a LRU algorithm, I believe.  If you have lots of memory, increasing
this buffer pool should automatically give you the effect of having a
RAM disk, as if the disk block that UNIX needs is already in a buffer,
no physical I/O operation will be requested of the disk driver.

       -roger