[Dovecot] mailbox format w/ separate headers/data

[John Tobin]

On Fri, Jan 22, 2010 at 09:03:42PM -0500, Charles Sprickman wrote:
> On Fri, 22 Jan 2010, Frank Cusack wrote:
>
>> On January 22, 2010 11:05:22 PM +0200 Timo Sirainen <tss at iki.fi> wrote:
>>> Dunno about zfs, but I've heard that at least in one NetApp installation
>>> deduplication was way too heavyweight.
>>
>> zfs dedup is pretty resources intensive -- for writes.  For mail I
>> suspect reads overwhelm writes?
>
> Sorry for the tangent, but I wonder if anyone here is running lots of  
> Maildirs on zfs?  I just recently started experimenting with it on our  
> backups server (FBSD 8.0), and I really am liking it.  I was also  
> surprised at how my little 4 drive raidz volume performed in benchmarks - 
> quite impressive.

We used to have our Maildirs on ZFS but we've moved to ext3.  ZFS worked
reasonably well, except for the days when it slowed down to less than
10% of normal throughput.  After a reboot or a couple of days of slow
running it would perform normally again.  This was on Solaris 10, at
most a couple of months behind on patches.  I had read the ZFS evil
tuning guide, and the ZFS best practices guide, but they didn't help.
It wasn't just mail that was slow - listing the contents of a small
directory could take over a minute.  We're much happier since switching
to ext3; I haven't worried about mail performance since.

-- 
John Tobin
"No no no. You're supposed to test with -march=... -fomit-frame-pointer
-ffancy-math -fuse-lots-of-resources-go-very-fast -fsacrifice-more-goats
-fsummon-cthulu-if-that-helps as root at nice -20, preferably in single
user mode and jumps should be aligned on pentagrams, not 8 byte
boundaries.
Definitely not use debugging :-)"
                                  -- Nicholas Clark, in perl6-internals