AFS gurus,
We have a professor who's hoping to implement our AFS cell (which as a
service, we call RFS, the Research File System) as his department's
solution for user home directories. After working on this awhile, he
thinks there may be a show-stopper. Is there an problem with using AFS
with applications that use mmap to solve IO-bound issues?
The problem is a esoteric issue called memory mapping. We have
applications that we use extensively in geophysics that use memory
mapping to improve performance. The relevant C function is "mmap"
(run "man mmap" on any unix or macos machine). Memory mapping is
used to reduce seek times when a program does a lot random access
IO, and is a well known performance trick for IO-bound applications.
Now I haven't written a simple test program to isolate the problem to
this specific issue, BUT I know that applications I use daily and that I
know use memory mapping fail when used on data stored on rfs. The
same application and data work fine when the files are local disk
files or
served by nfs. Thus the memory mapping hypothesis is a strong
possibility.
Is this a know limitation? If so, is there a solution?
We are running OpenAFS 1.4.11 on the server, and I am not sure what he
is running on the client side, but I'd imagine it's the latest stable
one on the openafs.org site. I'm also not sure which
type/version/kernel of Linux he's running on the server end.
Thank you for any help/suggestions.
Chris
