Clustering Load Balancing
Articles and Tips: qna
01 Aug 2002
Q.
The premise of the Virtual Server Load Balancing access to data volumes which are only mounted on one of the Cluster Servers does not seem possible. However, I am not all-knowing and therefore want confirmation from those who know much more than I.
From a customer... The question really boils down to this. Does the Cluster-Virtual Server dynamically load balance requests to the Cluster-Enabled Volumes when the volumes are configured in a single or a large pool scenario?
Novell's claim is that in a single pool configuration, the Virtual Server dynamically handles the distribution of volume load across all cluster nodes. From everything I have seen, it does not seem possible to distribute volume load/requests to a node that does not have the pool active and the volume(s) mounted. The only way for a particular cluster node to even access a pool and its volume(s) is for that node to have the pool active and the volumes mounted, which, as we know, only happens when the pool fails on that server.
I can envision the Virtual Server balancing the load of other Cluster Resources and Services, such as server-based applications, but not the volumes of a single pool that are active and mounted on a single server. So far, the only cure that I have heard for avoiding what I will term the "domino affect" (rampant application downing all cluster nodes) is to create multiple pools with associated volumes and not allow those individual pools to fail to all other nodes in the cluster. Is this correct?
Clustering Tom in Chancyville
A.
Dear Tom: You are correct. Novell's clustering solution is designed for high availability, not load balancing. Any resource (volume or application) is only active on one node at any time.
The "domino effect" analysis is also correct. If there is a problem with a resource that abends each node it get loaded on, all nodes will eventually fail. The work- around, as mentioned, is to not assign all resources to all nodes.
* Originally published in Novell AppNotes
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