VMware's Storage VMotion is a tool that brings the capabilities of virtual server migration to storage. Without interrupting users virtual machine data can be moved from one storage platform to another. It allows you to mix storage tiers and vendors more easily than in a non-virtualized environment. The missing link with this capability is all it can do is move data you need to know where to put that virtual machine.Storage VMotion movement can be across different storage tiers from Solid State Disk to SATA, for example it can even be across different manufacturer's storage systems. This is ideal as there are some manufacturers that you may feel are better for high performance storage and others that are better for high capacity storage. A Storage VMotion like capability allows for load balancing and right sizing the storage I/O of your environment, but you need a tool to help diagnose where those virtual machines should move to.

You may also want to use this type of capability to mitigate impact from a failing storage system. For example if one of your redundant power supplies has failed you may want to move some critical virtual machines to another storage system until it can be repaired. Another example may be if a drive has failed and a rebuild is occurring, in many systems the rebuild process will dramatically reduce the storage performance of the attached servers. While you could de-prioritize the rebuild job to minimize the impact to application performance but you do this with the risk that the rebuild will take too long to complete and another drive fails. With tools like Storage VMotion you can move all your virtual machines data or at least your critical ones and let the rebuild job have all of the storage processor to complete the rebuild much faster.

As we discussed in our article "Server Virtualization Monitoring Requires Objective Storage Visibility" the real key with taking full advantage of features like Storage VMotion is having a tool that will help you figure out where is the best location to move the virtual machine. This becomes especially complex if you have multiple types of storage and those types of storage are from multiple vendors. While some storage systems have relatively strong storage management software included with them most do not understand the relationship between their storage systems and the virtual machines. They may give you a view as to how the virtual host is using that storage but not the virtual machines on the host. Since that is the level of granularity that you will be working with that is really the view you need.

You also need to be able to see from the storage up to the virtual machine or from the virtual machine down to the storage. You'll want to be able to measure storage I/O utilization over a span of time to see what virtual machines are really able to take advantage of faster storage or would work just as well on slower, more cost effective storage. This way when the need to move a virtual machine's storage occurs you can quickly analyze what other storage platform is the best candidate.

Finally, if you are going to select a best of breed storage hardware approach, then you are going to need a tool that will can perform the above analysis across multiple vendor hardware platforms. A tool that can provide this in a single consolidated view but then also allow drill down to detail the specific storage systems. Storage VMotion is an amazing capability adding a tool that completes its missing link provides the storage manager the ability to better respond to the dynamic nature of the virtual infrastructure.

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George Crump is lead analyst of Storage Switzerland, an IT analyst firm focused on the storage and virtualization segments. Find Storage Switzerland's disclosure statement here.