The IBM SAN Volume Controller is a fantastic storage solution to virtualize storage arrays from different vendors, offer performance improvements, replication, compression, encryption and a huge interoperability support matrix.
However, one of the annoyances of IBM SAN Volume Controller architecture is if a single node has a hardware error, or requires maintenance you’re limited to a single node in the IO group.
This issue has now been alleviated by introducing the option of a hot-swap node for when a node is offline for an extended period.
A IBM Redbook has been published here which describes the process.
This function is to be extended in future releases of SVC code to allow an automated hot-swap node during a code upgrade. Historically in a 2-node SVC cluster, you’d be left with a single node in the IO group would would be vulnerable to a single point of failure for prolonged periods of time. With this hot-swap node feature, the spare node would be upgraded first, before replacing a down-level node as it goes offline for upgrade. This should significantly improve reliability of the SVC cluster during the upgrade process.