RIZZI@usc-isib@sri-unix.UUCP (06/06/83)
From: Bill Rizzi <RIZZI@usc-isib> Isn't is possible to use a RAM disk as a system device with UNIX? If so, disk speed may no longer be the bottleneck for efficient implementations. Bill (RIZZI@ISIB) -------
sdyer@bbn-unix@sri-unix.UUCP (06/06/83)
From: Steve Dyer <sdyer@bbn-unix> It's quite possible to use a RAM disk as a root (or swap) device for UNIX-- in fact, that's a quite popular way to bootstrap up a kernel before working disk hardware is available. Just write a software device driver which accesses a RAM partition instead of the disk. Trouble is, UNIX likes LARGE disks, so unless you have lots of RAM available, it doesn't buy one much. (I mean, it's OK for bootstrap purposes, but lousy for a production system.) And the amounts of RAM we're talking about (2-20mb) are still economically infeasible for most small systems, though this should change soon. Steve Dyer sdyer@bbn-unix
SJOBRG.ANDY%MIT-OZ@mit-mc@sri-unix.UUCP (06/07/83)
From: Andrew Scott Beals <SJOBRG.ANDY%MIT-OZ@mit-mc> Yes, you could configure a ram disk to be a system device for unix. It would be even easier to write a driver for that than for a regular disk, 'cause unix doesn't know about track and sectors, just blocks. -------
BYTE%mit-mc@sri-unix.UUCP (06/08/83)
From: Roger L. Long <BYTE@mit-mc> 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