NFS and transactions?

[Matthias Andree]

Chris Wilkes <cwilkes-bf at ladro.com> writes:

> On Wed, Jan 19, 2005 at 03:50:13PM +0100, Matthias Andree wrote:
>> 
>> Pure interest: what makes people want to use NFS for mail services in a
>> broader sense?
>
> I want to move towards that so I can have multiple mail delivery and
> POP/IMAP pointed at the same files:
>   IMAP1 \
>   IMAP2  +-> one NFS filesystem
>   SMTP1 /

That is hairy.

It can work with the non-transactional Berkeley DB store as long as:

1. fsync works

2. fcntl locking works

3. mmap works (this is especially hairy) or reliably reports an error on
   opening the database already so we can retry with DB_NOMMAP. We'll
   always do that if regular open fails, but this option isn't currently
   exposed AFAIR.

It will certainly *not* work properly with the transactional Berkeley DB
because the locking happens inside the environment and we'd need a
coherency protocol between NFS clients, which we don't have.

> Also then I can move my scripts that run every 30 minutes to check the
> "makespam" folder off from the IMAP servers themselves and on to the NFS
> server.

OTOH, if you have four servers (IMAP1, IMAP2, SMTP1, NFS1), just run
bogofilter and related stuff (training) on the NFS server only - that
simplifies things a lot because the IMAP and SMTP server aren't
accessing bogofilter's database.

-- 
Matthias Andree