Subject: Re: mbx performance

From: "Thomas Smith" <[email-masked]>
Date: Tue, 25 May 2004 20:59:40 -0700 (MST)

> On 4:30:58 pm 05/25/04 "Thomas Smith" <[email-masked]> wrote:
>> I converted all of my mbox mailboxes to mbx. I've noticed an increase
>> in performance for my web-based IMAP client. However, I continue to
>> have a problem that existed prior to the conversion.
>>
>> As I understand it, mbx is more memory efficient than mbox. This being
>> the case, shouldn't it consume less RAM while a mailbox is being read
>> by an IMAP client? This doesn't seem to be happening in my situation.
>> For example, I use SquirrellMail for webmail. There are system-wide
>> resource restrictions on RAM usage preventing any user from utilizing
>> more than 8 MB of RAM via SquirrellMail.
>>
>> My Sent folder would always exceed this amount when I selected "View
>> All"--there are over 3700 emails stored there. I continue to get the
>> error after the conversion to mbx.
>>
>> Am I missing something or did I misinterprete what I read?
>
>
> The 8MB restriction in squirrelmail is the PHP limit for script
> execution (php.ini setting). In the case of "show all" on 3700 messages
> squirrelmail is building a header list in memory of all messages, which
> combined with the other memory requirements of squirrelmail, pops the
> limit. Remember that in this case the IMAP client  does not care what
> kind of mailbox the IMAP server uses, it uses the same commands to
> retrieve information. A mailbox type with a zero memory footprint (in
> terms of the IMAP server memory usage) would still not alter the amount
> of memory the PHP script needs to store the fetched header values. I
> recommended to the squirrelmail developers not so long ago that they
> remove the "show all" links when the IMAP folder is over 500 messages,
> specificly to address this type of issue.

"show all" isn't the only time I've had the problem--it's also ocurred
with about 400 emails. I was able to "show all" but if I tried to forward
a message that contained a 1.2MB attachment SquirrellMail would generate
"memory exceeded" errors.

>From what you describe, SquirrellMail stored the header data of those 400
emails and when I tried to forward the 1.2MB email SquirrellMail fetched
it (while retaining the 400 emails' header data in RAM) and attempted to
load the additional 1.2MB into RAM--thus exceeding the 8MB limit. Sound
right?

---

From: "Thomas Smith" <[email-masked]>
Date: Tue, 25 May 2004 21:11:02 -0700 (MST)

> Thomas Smith wrote:
> why don't you see if you can use something like cyrus-imap instead of
> UW-imap.  I found it's much better.  I started using UW when I first
> started working on linux.  But after a while, I learned cyrus is a much
> better choice for performance and reliability.
> At least that's my opinion......see for yourself.

>From what other posters have written, it doesn't seem to be an IMAP server
issue. Rather, it's a SquirrellMail and PHP issue. SquirrellMail is
caching data in RAM and PHP's RAM restrictions are causing problems when
SquirrellMail loads large mailboxes.

I think a better choice for my situation would be to change webmail
clients to something more efficient. Or find ways to fine tune
SquirrellMail to reduce or eliminate these problems.

That said, as I've posted previously on another thread, my web hosting
provider uses a mixed OpenSource and proprietary setup. This makes it
difficult to load "custom" software. The decision I made was to optimize
what they've provided me to work with.