[Dovecot] extremely slow delete/move operations?

[John Peacock]

Gregory K. Ruiz-Ade wrote:
> The primary difference seems to be that we're using NFS here

<snip> 8<

> Mailbox formats are mbox.

Those are the two most important pieces of information in your message 
(IMHO).  mbox is always slower than maildir when the filesize exceeds 
the operating memory for the server (i.e. it cannot be mmapped).  NFS 
will always be slower than "local" access, even on NetApp's supposed 
'high-performance' NFS.  The combination is deadly, since every message 
stored in Trash requires copying the entire mbox file and appending the 
new message, then deleting the original and renaming the new file in its 
place.

Then there is the additional performance drag caused by Dovecot 
rewriting the index, as well as Thunderbird (which you should really 
upgrade to 1.5) keeping its local index up to date.  You can confirm 
this by emptying your trash folder and seeing if the performance changes 
(which I am confident it will).

There are three things you can do to improve performance:

1) Upgrade to Dovecot 1.0 stable (or even Beta2);
2) Switch to Maildir (instead of mbox);
3) Install a SAN (instead of the NFS mounted NAS).

The last is the only one that costs you hard capital; the other two only 
involve your time, which as we all know, doesn't count.  ;-)

HTH

John

-- 
John Peacock
Director of Information Research and Technology
Rowman & Littlefield Publishing Group
4501 Forbes Boulevard
Suite H
Lanham, MD  20706
301-459-3366 x.5010
fax 301-429-5748