On Wed, 24 May 2006, Dan Trainor wrote:
D Canfield wrote:
Perhaps I'm missing something obvious, but I would have assumed Maildir to
be *less* prone to consistency errors. I may not be able to say "here's
exactly what the server looked like at 11:59 on 5/23" but I don't see how
the backups would be invalid. I could see issues with mbox storage where
you'd start reading a large mailbox, and the server rewrites half the file
before you finish with it. Again, I may be missing something...
In any case, how would the LVM snap help me with the original problem?
Wouldn't I still need to backup millions of small files even with a
snapshot?
Thanks
DC
Ryan Novosielski wrote:
You'd almost need an LVM snap anyway, wouldn't you, for consistency's
sake? Seems to me Maildir is particularly vulnerable to inconsistency if
backed up while the server is running.
---- _ _ _ _ ___ _ _ _
|Y#| | | |\/| | \ |\ | | |Ryan Novosielski - User Support Spec. III
|$&| |__| | | |__/ | \| _| |[EMAIL PROTECTED] - 973/972.0922 (2-0922)
\__/ Univ. of Med. and Dent.|IST/AST - NJMS Medical Science Bldg - C630
On Wed, 24 May 2006, D Canfield wrote:
I'm just curious how other users are backing up maildirs using bacula.
We're using cyrus as our mail server, so we've got about 162GB of data
stored in 4.4 million files, or an average of 37K per message. Most
other products I've tried (both commercial and open source) have not been
too happy with this arrangement and end up requiring vast amounts of disk
space and overhead to index this kind of mail spool.
Does anyone know if bacula is any better with this? If not, I'm thinking
my best resort would be to have each user's mail spool gzipped before
backing it up (we don't restore individual emails for users, so this kind
of "resolution" is sufficient for us). Any ideas on a good way of doing
this that won't require me to run an external crob job to do the zipping
and require almost twice the disk space?
Any other insights would also be appreciated.
Thanks!
DC
Hi -
I think the point that Ryan is trying to convey is that an LVM snapshot would
be much quicker than any other product out there, including Bacula. You
could then archive that snapshot, and be sitting pretty.
I think Ryan suggested against Bacula for those 4.4 million files because it
would take a while, leading to inconsistancies. At least that's what I think
;)
THanks
I would think with all of those files -- granted I don't know the
internals -- you'd run into trouble. Aren't the index files kept someplace
other than the individual messages? If so, if it backs up the mail dir one
minute and the index another minute, you already have a confused mailbox.
In UNIX mailbox format, you backup the mailbox as it is -- it is entirely
self-contained. Of course, either case allows you to have a lack of
consistency across mailboxes... User A's mailbox might be backed up at
2:00 and user B's might be backed up at 2:45.
With LVM, at least you've frozen the snap. That doesn't necessarily help
your speed situation, but low speed + high rate of change is asking for
it, IMO.
---- _ _ _ _ ___ _ _ _
|Y#| | | |\/| | \ |\ | | |Ryan Novosielski - User Support Spec. III
|$&| |__| | | |__/ | \| _| |[EMAIL PROTECTED] - 973/972.0922 (2-0922)
\__/ Univ. of Med. and Dent.|IST/AST - NJMS Medical Science Bldg - C630
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