Cluster Confusion

Question

Hi,

      I am by no means a SQL Guy but was looking to clarify few doubts on SQL clustering. Please help me with below questions and elaborate if possible:

1) Default Fail Over cluster with 2 nodes in SQL server is done with shared storage, ideally a SAN or shared disk, right?
2) It can either be SAN or Mirror, both can't be used at single time and don't make sense, right?
3) I hear few people saying active / active is not possible with SQL Server while some say it's there, also there can be a multinode cluster. What's truth here?

Niraj

Answer 1

Hello Niraj,

1. With two nodes you can use other means, but SAN with Fibre drives are the default and MUST be used if you go to more than 2 nodes.
2. I'm not sure what you mean by SAN or Mirror. One is a storage technology and the other is a HA technology.
3. Most clusters are "active/passive" which is the view of the Cluster, not SQL Server. "Active/Passive" means that everything is running on one node in the cluster (Active) and the other is just waiting for the fail over (Passive). In SQL Server terms we use Single Instance or Multi Instance clusters. However most people will just say Active/Passive or Active/Active. Active Active Is possible and I have seen it used, however it means that you may have some performance degredation should any resources fail as one node will now be doing the work of two.

Hope this helps,
-Sean