[Dovecot] maildir on zfs (was: mailbox format w/ separate headers/data)

[Charles Sprickman]

On Jan 22, 2010, at 9:22 PM, Frank Cusack wrote:

> On January 22, 2010 9:03:42 PM -0500 Charles Sprickman  
> <spork at bway.net> wrote:
>> Sorry for the tangent,
>
> You should probably start a new thread when changing the subject.   
> Then
> you don't have to be sorry. :)

I figured I was already drifting OT for this list, so...  :)

>
>> but I wonder if anyone here is running lots of Maildirs on zfs?
>
> When you say "lots of Maildirs" I assume you mean filesystem-per-user?
> You can of course use "lots of Maildirs" yet have only a single zfs
> filesystem but that doesn't seem to me to be worth questioning.

No, I just meant a large number of users using Maildir (rather than  
mbox, dbox,
whatever else) on a single ZFS filesystem.  Although filesystem per  
user is
an interesting idea.  When my personal box gets upgraded to FBSD 8.0,  
I may
try that for fun.

>
> I am running that way but it's less than 100 users so probably not  
> what
> you would consider "lots".
>
>> I'd seen some comments here in the past that zfs+maildirs = bad.
>
> I can't imagine why that would be the case.  There are some problem
> loads for zfs (zfs-backed NFS writes, e.g.) but why maildir would be
> particularly singled out I wouldn't know.

I think this is the message that got stuck in my head:

http://www.mail-archive.com/dovecot@dovecot.org/msg25478.html

I *think* that when I was doing my massive week-long google binge on zfs
I read a few comments about zfs being "non-optimal" for email.  It's  
"teh
internets" though, and it could have been someone just talking out their
behind or it could be talking about a much earlier release of ZFS.

I have a small backups box that's got just 4 WD RE3 drives on it.  The
benchmarks for this thing pretty much blew me away.  We're not talking
top of the line hardware here and it was performing at least as well  
as a
good Areca or 3Ware hardware RAID setup.

Anyhow, if I find more places to run ZFS in production and it seems  
stable
enough, I'd like to try getting it running on my big mailserver at  
some point.
Backing up from UFS to ZFS using rsync is fine, but ZFS send/recv  
looks like
a far more interesting backup solution.

Charles

>
> For filesystem-per-user, if by "lots" you mean 1000 or 1000s then you
> have the problem that it takes forever to mount all of those  
> filesytems
> on reboot.  That's not a maildir-specific problem though.
>
> -frank


Charles Sprickman
NetEng/SysAdmin
Bway.net - New York's Best Internet - www.bway.net
spork at bway.net - 212.655.9344