Clustering ListManager

What is ListManager Clustering?

Multiple ListManager instances (or nodes) may be clustered together using a single database. Each node can perform all ListManager tasks: receive and send mail, accept and process clickthrough and other tracking, and perform scheduled tasks.

The benefits of a clustered ListManager environment are:

• True load distribution -- Any node can perform any task, including sending mail, receiving incoming mail, accepting tracking events or performing scheduled tasks.
• Redundancy-- If one node goes down for any reason, others will pick up the work.
• No single point-of-failure -- No single critical ListManager system must be working for the cluster to function (other than the database server).
• Improved bounce processing speed -- Processing and saving bounced mail in the database is faster.

What happens when a ListManager node fails?

If a node is lost for whatever reason, the task the node was working on will be interrupted until the node is restored. If the node was delivering mail, no data will be lost, but some recipients will not receive mail until the node is restored. Depending on the sending speed of the lost node, the number of recipients delayed may be in the low thousands.

What do I need to cluster ListManager?

In addition to the hardwareand software requirements for a single ListManager installation, the following is also required:

• An MSSQL or Oracle database. ListManager clustering is not supported for MSDE.
• A separate database server with ample hardware to handle the load of multiple ListManager nodes. ListManager clustering is not supported when one of the ListManager nodes is on the same machine as the database server.
• A LAN. Clustering ListManager on a WAN is not recommended.
• Adequate hardware for each ListManager node. Each node must run on its own machine; two nodes may not run on the same machine. Optimally, the hardware should be the same for all ListManager nodes to make configuring the nodes easier, though not strictly required. Different nodes may use different platforms if connecting to an Oracle database.
• Clustering license(s): The serial code for additional ListManager nodes must be enabled for clustering. If a node has no license, or has a license for which clustering is disabled, it will be disabled. Contact sales@lyris.com for more information about purchasing clustering licenses.

How difficult is it to use and administer a ListManager cluster?

A ListManager cluster should be largely transparent to users. The administrator may need to initially configure some IP and DNS settings for each node in the cluster, but otherwise administration of a cluster will not be significantly more difficult than administration of a single ListManager instance.

Will I see increased sending speeds from a cluster?

Depending on the licenses, a cluster can potentially send out mail more quickly than mail from a single ListManager instance. However, keep in mind that ListManager cannot control how quickly ISPs will accept your mail. In some cases, an ISP will limit the number of inbound connections not just from a single IP address, but from an IP block or range.

Where can I see the performance of nodes versus the cluster?

In Reports: Server Performance: Server Sending Speed, you may view charts displaying the attempted, successful, and failed messages per hour for individual nodes or for the cluster.

Can I cluster the database?

ListManager does not include tools to run against multiple databases. However, your database may be clustered so that the database clustering is transparent to ListManager. Contact your database vendor for more information about database clustering.

Can there ever be conflicts?

Normally, each node in a ListManager cluster will pick up tasks as they are created, and there will be no conflict between them. In rare instances, two moderated messages could be approved twice from two separate nodes, causing a posting to be sent twice. To eliminate the possibility of such mishaps, have list administrators use the interface from one of the nodes.

Important Clustering Notes

• Message recipients may receive duplicate messages in a cluster if the same message is posted to multiple lists and/or segments. Duplicate messages will be received even if the list(s) are set so members will not receive crossposted duplicates.
• To send the same message to multiple lists and segments, send to each list and segment separately, purging out recipients of earlier messages on the Mailings: New Mailing: Recipients tab.
• Recency limits may also be ignored if a second mailing is approved before recipient list processing for the first has been completed.
• You may not select which node a message is sent from; ListManager distributes messages across the cluster automatically.