Subject: nfs caching
To: None <tech-kern@NetBSD.ORG>
From: Ron G. Minnich <>
List: tech-kern
Date: 02/26/1997 11:11:08
chuck cranor forwarded me a note via tech-kern about an nfs file caching
question. The writer was proposing caching in the MV.  He thought I ought
to mention the autocacher I did in '89, which was written up in ( in
think) '91 winter usenix. 

Anyways the autocacher ran like an automounter, save when you read files 
they were copied to local disk and cached from there. I like the way it 
works better than the solaris cfs; you can read the paper to see why 
(it's on my web page: see below URL). In particular in solaris CFS since it 
is a block cache there's lots of concerns re integrity, so that for 
example you need to 'cfs_fsck' the cache when you come up. CFS is just too 
complicated for my taste. I note that I haven't found that many people 
actually using it: they seem to be scared of it for some reason. 

I think I prefer whole file caching to to caching in the vm as the earlier
post proposed. Statistics I accumulated over ~100 machines show that if
you have, e.g. a 1 GByte /usr/local, for any given user you only need to
cache 5-10% of that (this is the high end), even using whole-file caching.
That's $10 of disk. 

Ensuring that up-to-date files are being accessed is trivial, of course. 

I had a version of autocacher that was implemented as patches to amd, if 
anyone wants it. It will need work as the code is so old.


Ron Minnich                |"Failure is not an option" -- Gene Kranz       | -- except, of course, on Microsoft products
(609)-734-3120             |