Path: utzoo!utgpu!water!watmath!clyde!cbosgd!mandrill!nitrex!rbl
From: rbl@nitrex.UUCP ( Dr. Robin Lake )
Newsgroups: comp.unix.wizards
Subject: Re: /dev/swap - possibility of it being a ramdisk
Summary: /dev/swap as a ramdisk has been evaluated
Message-ID: <585@nitrex.UUCP>
Date: 11 Dec 87 20:20:35 GMT
References: <712@qetzal.UUCP>
Reply-To: rbl@nitrex.UUCP ( Dr. Robin Lake )
Organization: The Standard Oil Co., Cleveland
Lines: 36

In article <712@qetzal.UUCP> rcw@qetzal.UUCP (Robert C. White) writes:
>Hello Wizards,
>
>Watching my poor little unix boxes swap, it occurred to me:
>why not utilize some extra ram to implement /dev/swap? It seems that
>the machine would speed up quite a bit, and hey, extra memory
>is pretty inexpensive, at least for the smaller 
>unix boxes. Also, it would be tactically easier to
>increase the amount of "swap" memory as opposed to repartitioning
>my disks, or mounting a disk pack under /tmp or some other 
>horrid kludge.

About 10 years ago, I was involved with the design of a "solid-state disk"
--- a ram disk that looked like a fixed-head disk for PDP-11 Unibus
machines.  A graduate student of mine did his Ph.D. dissertation on the
performance of UNIX with such a box. (Sugit Kumar, Case Western Reserve
University).  Bottom line was that you want TWO such "ramdisks", one for
/tmp or /usr/tmp and one for the commonly used programs (/bin, /usr/bin).
The only shortcoming is that the device drivers and the I/O strategies of
the kernel consume relatively huge amounts of time per "disk" access.  The
result is that a solid-state device (17,000 times faster transfer rate
than a rotating disk) only performs 10 to 50 times better.

Nonetheless, watch for significant new computer architectures from the 3-letter
computer vendors which take advantage of more ram memory than you might have
ever believed would fit in a box!  Exciting times ahead....

Rob Lake
BP America R&D
(ex-Principal Scientist, Monolithic Systems Corp  - mfgr. of "Extended
Memory Unit" )
decvax!mandrill!nitrex!rbl
216-581-5976
-- 
Rob Lake
{decvax,ihnp4!cbosgd}!mandrill!nitrex!rbl