[529] in Info-AFS_Redistribution
Re: some questions about using AFS to share core OS files
daemon@ATHENA.MIT.EDU (Wallace Colyer)
Thu Jan 16 11:45:51 1992
Date: Thu, 16 Jan 1992 10:07:35 -0500 (EST)
From: Wallace Colyer <wally+@andrew.cmu.edu>
To: Info-AFS@transarc.com
In-Reply-To: <8dRAQ2f0BwwbI0gIxN@transarc.com>
If you have multi-user workstations it is important that as much of the
"often-used" software is kept on the local disk and not AFS. The AFS
cache manager has major concurrency problems on multi-user workstations.
In addition, though cache hit rates are often seen as high percentages
it is difficult to assess whether they are good or not. One reason for
this is the use of paths with large numbers of elements. For software
on the Andrew cell you may go through a path that looks like:
/afs/andrew.cmu.edu/system/beta/pmax_ul4/local/lib/gnu-emacs/bin/loadst
Now, ignoring that there symlinks involved here in reality changing the
state, if I have already run gnu-emacs the path up to loadst is already
fetched and in the cache, so even though the file I want is not in the
cache, the hit rate is still 90%. This is because 9 elements in the
path were there when the file was fetched. If I then access the file
again immediately after it is fetched the rate goes up to 95%. It is
easy to see how quickly the hit rates mean nothing. On our multi-user
machines we have seen 98% and 99% hit rates, but I don't know if it is
good or not.
-Wallace
