[KLUG Members] NFS / server tuning for mail storage?

[adam bultman]

I'm using maildirs, so I don't have to even worry about the problems 
that arise from having mbox-style storage (i.e. having two processes 
trying to access the same file).

Moving to cyrus at this point isn't an option; and besides- last time I 
investigated cyrus, their directory naming was just... wierd..    
Maildir at least gives me identifiable directory names (last time I 
fiddled with it, directories were named 1,2,3,4,5. ,etc)

I'll plow ahead,  and note any problems I run into.  I know other people 
who are doinig the same thing I'm attempting - one of them on this list 
- but the only difference is they have a bit more power in their 
mailservers.

Adam


Bruce Smith wrote:

>Cyrus-IMAP solves the problem by keeping each message as a separate
>file, that way the system doesn't have to read through one huge mbox
>file (the entire folder) each time to read/delete/move a single email.
>
> - BS
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>>Having solved my courier-imap/vmailmgr, then having moved to qmail-ldap
>>with courier-imap/pop3, I'm getting farther along in my testing and
>>noticing that when mailboxes get larger than a few thousand messages,
>>the mailbox is effectively useless.
>>
>>The server will either spend time with imapd at about 10% usage, with it
>>waiting on the network, or imapd will take up ALL the cpu, and spin for
>>quite some time.
>>
>>My configuration is this:
>>
>>Netapp, with gigabit connection to the switch.
>>
>>Server: 800 MHz serverblade, 512 MB RAM, 100Mbit connection to switch.
>>
>>-
>>My plans are to use LVS and balance say, 3 to 4 servers from the 800 to
>>1200 MHz range handling mail services, with them all connecting to the
>>netapp back end via NFS.
>>
>>But my fear is that people are going to have huge mailboxes, imapd will
>>sit for minutes on end, the users will get frustrated, and then complain.
>>
>>Are there more effective NFS options for these servers to use?  Right
>>now, I'm using soft, noatime, tcp as my options. I don't know if using
>>TCP is any *faster*, or if setting the rsize or wsize will help any either.
>>
>>Furthermore, should I be splitting up my services? The 1200 MHz systems
>>will have 1 G of ram instead of 512, should I use those for imap/pop
>>processing and the slower, 800 MHz systems for SMTP?
>>
>>Any ideas would be most appreciated. I've worked pretty hard on this,
>>and I'm wondering if there's a fundamnetal speed problem that I won't be
>>able to overcome with more serverblades, or if there's other ways I
>>could squeak more performance out of them.
>>
>>Adam
>>    
>>
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