We've been wrestling with a resource utilization problem on our cluster of
6 vpopmail servers.

What we're seeing is that our network and RAID 5 IDE-based disk array on
our central mail store server is not able to keep up with the 'client'
servers doing the POP3, IMAP, Webmail, and SMTP legwork. We're seeing
usage spikes on our RAID controller up to about 105% of its duty load.
Also, we're getting a lot of NFS errors in the logs on our client servers.
This results in the odd SMTP / POP3 error as the NFS connection fails.
Network traffic does occasionally spike up to the 12mbps limit of our 100
base network connection.

This mail store server is responsible for the store of the
vpopmail/domains directory (NFS mounted by the 'client servers') and run
SQL select queries to verify passwords... The read / writes on the disks
are reaching the limit of the IDE RAID controller and the 100-base

All of this together has us looking at replacing our IDE / 100mbit based
mail store server with a U320 SCSI machine and gigabit ethernet.

Before we take this costly step, what have you noticed for user / system
loads before you start hitting the limits of your hardware? Should we be
having these issues with about 15,000 email users and 5 front-end 'work'


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