[IMail Forum] Imail High Availability Setup

[Randy Leiker]

Hello everyone,   I'm working on a project with a goal of making Imail a high availability service. I'm aware that Imail does come with support for "peering" (setting up multiple Imail servers to listen to each others messages & use store & forward when a Imail server goes down), but I'd like to take it a few steps further.    I'm strongly considering setting up the following:   1) Two Imail 8.0 servers will be setup, but completely unaware of each other (in other words, Imail's peering feature will not be used).    2) Two load balancing devices, such as Cisco's LocalDirector will be placed in front of the two Imail servers.   3) Behind the two Imail servers, an iSCSI disk array will be setup. Both Imail servers will have direct access to a common storage pool on the iSCSI disk array and will essentially be able to see the same set of files (i.e. shared storage or similar to mapping several computers to a single drive on a server).   4) Appropriate DNS records will be setup so that both the MX records point to the load balancers.     But, here's the question: I have little doubt that both servers can effectively load balance the SMTP traffic.  However, when it comes to the Pop3 or Imap4 service, Imail tends to put a lock on a user's mailbox file while a message is being delivered. What happens when one of the Imail servers has locked a user mailbox for writing & the other server tries to simultaneously write a message to the same mailbox?   I'm taking an educated guess that the second Imail server will see a lock & will just hold the message until the lock is removed by the other Imail server, then try to deliver it's message.  But, I'm just not certain.  I spoke with Ipswitch tech support earlier today & learned that they "don't officially support this type of setup," however the tech admitted to me that she has had customers call in & say that they've been able to successfully set up this type of configuration.  Supposedly Ipswitch will begin supporting this type of arrangement by the end of the year.  In the meantime, I'd really appreciate hearing from any of you out there who have somewhat similar setups & pitfalls to watch out for.   Randy Leiker  ( [EMAIL PROTECTED] ) Skyway Networks 816.221.1400  Ext. 100 Toll free: 1-800-538-5334 http://www.skywaynetworks.com