John Peacock wrote:
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).
Well, this is something that I cannot change. We're stuck with mbox for now. The last time I used dovecot (at my previous job), dovecot out-performed UWIMAPd on the same mbox mailboxes, so why it's the other way around is beyond me...
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.
The thing is, these mail servers _are_ the local storage for the mail spools and home directories. There is no network involved when dovecot is accessing the INBOX or saved mail folders. Yes, they're "NFS" mounted, but this is RHEL4 (linux 2.6.x), and when an NFS share is mounted from the local host, it's done as a bind mount, which means local disk access.
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).
Should I then wonder about turning off Dovecot's indexing? If that's a "performance drag"...
Upgrading Thunderbird may not be so simple, either. These same clients were having much faster response times on a Sun E450 running Solaris 2.8 and UWIMAPd with the same logical setup (NFS mail spool and home directories mounted from the local system). Our Windows users can be more easily upgraded to later clients right now than our Linux/Unix users
There are three things you can do to improve performance:
- Upgrade to Dovecot 1.0 stable (or even Beta2);
I wasn't aware there was a 1.0 stable yet.
- Switch to Maildir (instead of mbox);
Not an option.
- Install a SAN (instead of the NFS mounted NAS).
As much as I may wish for it, it's not an option either. And, I point out again, that the mail servers have the necessary filesystems _locally_ mounted, by automount, via bind mounts:
gruizade@csefast(pts/22):~ 21 > mount | grep gruizade /export/homes1/gruizade on /home/gruizade type none (rw,bind)
I will work on testing 1.0 beta2 for now...
Thanks again,
Gregory
-- Gregory K. Ruiz-Ade Sr. Systems Administrator Computer Science and Engineering University of California, San Diego Office: EBU3b 1216 Phone: (858) 822-2625 E-mail: gkra@ucsd.edu