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Hello Mark,
Saturday, May 05, 2001, 9:18:09 PM, you wrote:
> Their reference to being NFS safe is to the fact that they use
Maildirs
> instead of a one big Mailbox which was been the Unix standard for a
long
> time. Vpopmail doesn't add Maildir support, it comes with Qmail and
is
> recommend by the Qmail install. The authors of Vpopmail just made
the
> logical choose to use Maildirs in their implementation.
I was assuming every sysadmin seriously running qmail (and that is the
case if you're going to build a POP cluster, I think) would use
maildirs as they are recommended and mailbox is obsolete.
> The reason the mailbox format does not work reliably across an NFS
share is
> because it is one big file that is constantly being written to as
the user
> reads and deletes mail and more comes in. Across an NFS share this
causes a
> problem because it is hard to prevent the file from becoming
corrupted.
> Since Maildirs contain one file for each new message you do not have
to
> worry about the file possibly becoming corrupted as new mail comes
in while
> a remote user is editting their mailbox contents. Also if the a file
becomes
> corrupted it only contains one message not 100's.
Exactly. And for exactky this reason, there are even people who use
sendmail
with maildirs. Mailbox is hardly anymore needed in todays environment
as most people won't access their mail via UNIX mailclients expecting
to have direct access to the mailbox.
> If you use Maildir format instead of a mailbox it does not matter
whether
> you are running vpopmail or some other program, it is the mail
delivery
> structure of your MTA that makes it viable over NFS not vpopmail.
Don't get
> me wrong, I am not putting down vpopmail. I use it and it is great.
Inter7
> has some excellent addons to Qmail.
This essentially doesn't matter in the day to day work but you're
point is valid. OTOH, the splitted directory structure is a sure
plus point for everyone who wants to build clusters.
> As for single point of failure. NFS is not distributed so if the
machine
> that has the mail directories goes down it is still a single point
of
> failure.
I know. I've been searching for solution that could reliably replicate
mailservers on filesystem level in realtime for long. There doesn't
appear to be any real solution on FreeBSD (as I can't get coda to
run).
> You> could get around this by using a raid array that can be
> accessed by multiple systems so if one goes down the other can still
access
> your raid.
I heard some people hacked qmail/vpopmail/whatever to deliver the data
to
two maildirs on separate servers. While this can be pretty easily
done, a general filesystem replication would suit me better as I could
use it for other stuff than only mail...
Best regards,
Gabriel
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