Tuesday, February 1, 2000

AS/400 partitioning for Domino servers


By Al Fishel and Jon Johnston

In October 1999, we discussed the AS/400 for Domino platform from a non-technical perspective (see http://www.dominopower.com/issues/issue199910/as400001.html). This article goes into more depth about Domino for AS/400 and covers a major reason you might want to use AS/400 as a Domino platform: server partitioning.

Partitioning versus clustering

The Enterprise version of the Domino server allows for partitioning or clustering of Domino servers. Domino administrators, particularly those working with NT-based servers, are more familiar with clustering than partitioning.

"NT server farms are commonplace, and the AS/400's capabilities are not overstated. It is one of the most reliable server environments in the marketplace."

For those unfamiliar with the terms, clustering is the grouping of two to six servers so that they appear as a single resource. Clustered servers are mirrors of one another; all databases are replicated between each server in the cluster. Clustering is implemented for the purposes of user and application failover and load balancing. Clustering provides automatic failover by allowing clients to automatically switch to one of the other servers in the cluster should the primary server fail.

Splitting the user base between the cluster servers can provide load balancing. Given a base of 5,000 users, each individual server might be configured to handle a maximum of 2,500 users. Users attempting to connect to the cluster once the 2,500 limit has been reached on a single server will automatically be attached to another server in the cluster. The user does not know or care which physical server in the cluster is providing service.

Clusters are associated with providing mirrored (redundant) services between physically separate servers. By comparison, partitioned servers are separate configurations of servers running within a single platform. While several of the Domino platforms support partitioning, partitioning in this context is most prevalent on the Unix and AS/400 platforms.

The AS/400 is unique in that it provides an environment in which you have complete control over the priority and resource utilization of each of the partitioned Domino servers. Up to 30 partitioned Domino servers can be installed on a single AS/400.

On the AS/400, each Domino server is installed into it's own subsystem. Each subsystem may be independently configured for memory and task allocation. This means that you can control the amount of memory each partitioned Domino server is allowed to consume, as well as set the priority level at each Domino server will run. Since each subsystem can be managed independently, each Domino server can be brought up or taken down without affecting the other Domino servers running on the AS/400.