[Gllug] Large mail files was -> RedHat

Dave Cridland [Media UK] dave.cridland at mediauk.com
Mon Nov 5 23:00:23 UTC 2001


(Pardon the Outlook, but Evolution crashed. Again. :-)

----- Original Message -----
From: "Steve Nicholson" <steve.nicholson at yoursolutions.com>
> > You want to run it on some kind of Journalling FS for best results, or
> > else you'll need to chattr +S a few places. Which is the downside.
> >
> > Of course, you can ignore this, but at your peril - Cyrus doesn't like
> > the FileSystem from vanishing beneath it in mid-write very
> > much at all.
>
> This is a little off putting for me at the moment, I haven't played with

Don't be put off, it's all a lot easier than you might think.

FWIW, I run without those precautions on my mailserver, and have had no
problems at all. This is, however, taking my life in my hands, and I
wouldn't advise it to anyone else. In other, more mission critical
environments, I've opted for the halfway house of running "sync" every
minute. This was, incidentally, before journalling FSs were available for
Linux (ie, ~3 years ago.)

But really, the only reason I haven't upgraded my current more-or-less
personal mailserver to Ext3 is sloth.

> journalling FS, my /var is a separate partition so I guess I could do
> this. Can live ext2 be converted to Journalling FS ok (taking necessary

Yes. Ext3 does this very nicely (and back again), without reformats.

What actually happens, as I understand things, is that Ext3 just creates a
"magic" inode without a directory entry, which holds the journal.

If you lose power, and the box comes back up treating the filesystem as Ext2
for some reason, then you just end up with the journal in /lost+found, and
Ext3 will (presumably) recreate the journal if you delete it.

It's a hack, but a damn fine one.

> backup precautions in case of problems obviously).  Is Resiser FS ok to
> go with now or is there another I should be looking at?  Didn't SGI
> release theirs?

ReiserFS is, well, interesting. I've run into problems, especially when
using it as a root FS. According to the website, I've just got duff
hardware, although the hardware runs fine on any other filesystem I've yet
to try. Hmmm.

Current thinking appears to be that Ext3, while slower, is definitely more
stable.

Cyrus's mailstores assume that filesystems are poor with multiple accesses
to lots of small files, so although the multiple file aspect of it will lose
you space, it won't actually have much of an impact on speed, since metadata
is all held in other files.

So essentially, there's no point in using ReiserFS for this particular job,
since Cyrus has worked around the common deficiencies.

As for the other Journalling FSs, I haven't used them, but what with Ext3, I
won't bother, either.

>
> > The RPMs for RedHat are very good, and downloading the source and
> > installing from that is fairly easy.
>
> I'm using Debian, will do a search on Google to check if there are any
> issues with this.
>

The worst case is really that it'll be badly configured, and some features
may not be set up. The man pages for Cyrus are very good, though.

> Dave thanks for all the useful information really appreciated.

Oh, one more handy tip - you'll have email in the old mailstore.

Best way to get it into the new mailstore is by fetchmail feeding directly
into LMTP, but for that you need the plaintext passwords - which you really
need anyway at some point to feed into the sasldb.

Second best way of doing it is to write a Perl script which singles out the
old mails directly from the mailstore, and feeds them into Cyrus's deliver
program.

For obvious reasons, redirect the delivery to use LMTP first with either,
and with the second, switch over POP3 and IMAP ports to Cyrus. You should be
able to do the entire upgrade with virtually no downtime. (Including the
filesystem upgrade, scarily.)


-- 
Gllug mailing list  -  Gllug at linux.co.uk
http://list.ftech.net/mailman/listinfo/gllug




More information about the GLLUG mailing list