Problem while deleting mailbox on a private spool on NFS
amilivojevic at pbl.ca
Fri Mar 18 11:04:15 EST 2005
Michael Loftis wrote:
> Don't use Cyrus over NFS. It's not safe. You *WILL* end up with
> corrupt mailboxes.
> There might be some NFS Client+Server combinations that are safe, but
> since you've a Linux client I'm guessing your NFS server is also Linux,
> a known not-safe configuration. The reason is file locking doesn't'
> really work on NFS.
Plus, couple of days ago I stumbled accross data corruption problem when
file on NFS mounted partition is mmaped on Linux client (CentOS 4, which
is RHEL 4 clone, kernel 2.6.9-5.0.3.EL). Quick grep of Cyrus sources
shows that Cyrus uses mmap in several places in the code, and I would
guess DB libraries also make use of it. So even if the file locking
worked, there are more severe problems on Linux NFS clients. This might
or might not be connected with the problem OP experienced. Basically,
people running Cyrus over NFS on Centos4/RHEL4 (and probably other
distros) should get a bit worried.
I found the problem when experimenting with one small app for creating
nul-filled files that is good candidate for "the most stupid use of mmap
that can trash your PC just like that". Note that I haven't got
confirmation that folks over at Red Hat were able to reproduce the
problem. I tested with single NFS client and single NFS server, so
there is probability that the problem is not general and exists only in
specific configurations. More info at:
Aleksandar Milivojevic <amilivojevic at pbl.ca> Pollard Banknote Limited
Systems Administrator 1499 Buffalo Place
Tel: (204) 474-2323 ext 276 Winnipeg, MB R3T 1L7
Cyrus Home Page: http://asg.web.cmu.edu/cyrus
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