[Dirvish] Excessively Long backups on a Postfix Mailder vault with Dovecot as the IMAP server

Paul Slootman paul at debian.org
Wed Mar 19 18:22:49 UTC 2008


On Wed 19 Mar 2008, Damian Cunniff wrote:
> 
> I am using Linux for both the backup server and the mail server.  My
> apologies for not clarifying that.  The file system is ext3 and the
> operating system is Ubuntu 6.06 Dapper Drake.  We are using that because
> it is 'Long Time Support' and we want to take advantage of that support.
>   Unfortunately it means that the most current software is often
> unavailable.  I did upgrade to rsync 2.6.9 (protocol 29) so that I could
>   preserve the ACLs on both my Windows and Linux boxes.  I was able to
> find a backport of that version.  I'll have to search for a backport of
> the 3.0x version or build one myself.  I'd rather have the package though :D

What version of libc6 is on that system? As it's Ubuntu (Debian-based),
I should be able to supply a compatible 3.0.0 package...

> At first I thought you were saying indexing the files is the problem,
> but when I looked at this output it only took 44 seconds to build that
> index.  On second thought I think that you're saying the actual
> comparison of the files to see if they need to be transferred is what is
> taking so long.  Is this correct?

That 44 seconds is pretty good. Of course, that's on one side of the
transfer (I believe rsync reports the sending side). Are you also using
that same Ubuntu on the dirvish server?  I'm wondering if some form of
filesystem fragmentation on the dirvish server may be slowing things.
Watching the cpu usage on both sides during the backup may help (is
mainly one of the systems IO-bound? Which one? Is memory getting low?)

BTW, for maildirs it may be useful to turn on the whole-file option in
dirvish, as files will generally not change. OTOH a file with the same
name but with different attributes will probably not happen often
(perhaps IMAP indices or so).


Paul


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