Hu's Blog

Yesterday, Hitachi announced the ability to cluster USP V/VM for high availability and non disruptive migration between current and future USP V/VM storage controllers. 

Since the USP V/VM is able to virtualize external storage, this will be the first continuous availability solution for both internal and externally  attached heterogeneous storage, all under  common management.

In fact this ability to cluster two separate control units over distance requires an  external disk attached to both control units to act as a quorum disk.  If the link between the two storage nodes is broken the quorum disk helps to identify which node is the correct node and which node needs to be fenced off.  If the quorum disk was internal to either of the two controllers it would not be able to provide the quorum function. So storage virtualization is required to make storage clustering work reliably.

What is the difference between High Availability Manager and business continuity solutions like TrueCopy and Hitachi Universal Replicator? The difference is that the secondary USP V/VM can be accessed immediately with High Availability Manager when the primary USP V/VM goes down for any reason.  With TrueCopy and Hitachi Universal Replicator, the applications have to be restarted on the secondary USP V/VM.

Imagine the work that is saved when a VMware server running multiple applications, can simply switch paths to a secondary storage controller when the primary storage controller fails.

In my next post I will talk about the benefits this provides for device migration.