SUMMARY: IMAP/POP Performance Question

From: Mark Mellman (
Date: Mon Feb 22 1999 - 21:20:42 CST

One line summaries of the replies that I received:

Sendmail is a resource hog, use qmail.

Outside causes, for example casional DNS logjams?

Large POP mail boxes causing long read times which appear as

The Veritas mount option for 'delaylog' can cause significant
performance problems.

Thanks to:

John White <>
Nickolai Zeldovich <>
Richard Goerwitz <Richard_Goerwitz@Brown.EDU>
Harry Levinson <>
Frank Smith <>

--------------------------------- Original Post

Hi Sun gurus,

We have a two processor E250 with 512 MB RAM and internal 4 GB disks
using Veritas FS and VM as our mail server. It receives mail via
Sendmail and clients access the server via POP3 and IMAP (Netscape,
Eudora, etc.) to read their mail. We also have Netscape's LDAP server
running on this machine.

There have been some intermittent performance problems on the server
lately and I would like to see if I can get some advice from the
experts. The trouble shows up as intermittent time-outs and long pauses

on the client side. While monitoring performance on the server when
there are problems, there appears to be a lot of disk I/O, but the
numbers are not that outrageous. There are approximately 200 IMAP
connections and numerous POP connections when the problem occurs. There

are no messages in any of the logs complaining about anything.

Services in use:

Public domain IMAP
Public domain POP
Netscape LDAP Server
Sendmail 8.9.1

Can anyone think of where to look next? Could it be the IMAP/POP
servers having scaling problems? Like I said, there are no memory,
cpu, network or swapping problems, just some busy disks.

Thanks in advance and as usual, I will summarize,

Mark Mellman

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