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Quoth Andy Mell on Tue, Jan 28, 2003 at 13:26:45 +0000
> The main problem appears to lie in replicating /var/mail/<mboxname> across
> multiple servers. These files need to be kept in sync and accessible from
> imapd/pop3d. NFS is apparently not a good idea for this due to the locking
> issue. How can this be dealt with without NFS??
I think you misunderstood what I said about NFS. It is a bad idea to
the the exim spool of messages on NFS -- that is the spool where the
Exim puts message BEFORE it delivers them.
The delivery spool -- where the mails are delivered so that users can
access them -- can and should be on an NFS server. However, the locking
problems are there so that you have to use MAILDIRS instead. It works
fine with courier IMAP, POP, etc...
> Someone suggested maildirs with Courier-IMAP but how does this help us
> avoid using NFS and locking?
It avoids it because it delivers one message per file and thus there is
no chance of two processes acessing the same file at the same time.
Dir writes are atomic operations and therefore you are safe there.
> A Netapp filer also uses NFS surely?
Netapp rules!
> Is NFS locking _really_ a problem?
Nope, provided you use maildir and not for the exim spool.
> I have to come up with reasons for my boss why we shouldnt switch to a
> product which claims to support full email redundancy. i.e. Lotus notes
> replicated servers, Oracle Collaboration Suite email server. I know I know,
> but hard facts are needed...
I amnaged the Freeserver cluster (3 millions subscribers?) for nearly 3
years and we never lost any emails. That's not true, we did lost about
2000 odd when the filer crashed with such a seriouse bug that even
Seagate could not figure out what this insane drive was doing.
The system runs L4 swtiches, Linux servers and Exim. That should be a
good case study!
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