How vSphere Storage vMotion works in a virtual environment

VSphere Storage vMotion is a new feature in vSphere 5 that allows the migration of storage from one array to another. Before this feature, migrating storage was a burden because it required scheduled downtime, additional migration programs and the remapping of storage to servers. However, in order to reap the benefits of Storage vMotion, it must be used in conjunction with either vSphere Enterprise or vSphere Enterprise Plus, as well as vCenter, VMware's management platform. In this video from TechTarget's Storage Decisions Houston conference, Founder and Chief Scientist of Howard Marks explains how vSphere Storage vMotion achieves the smooth migration of virtual machines. Watch the video or read the transcript below.

One of the best features of VMware and of Hyper-V, [in my opinion], is the ability to move storage.

VMotion is cool; vMotion lets you move a server from host to host. Storage vMotion lets you move the storage for a server from storage array to storage array. Now, what's the lifetime of a storage array in your environment? Three years, maybe five? Certainly nobody goes 10.

If you're dealing with EMC or HDS or NetApp, the maintenance will cost you 15% of the retail price of the product for the first three years, and then 25% for the next two years -- and then they just won't sell it to you anymore. So that means every five years or so you have to move your data from one array to another. Before virtualization, that was a royal pain. You had to schedule downtime; you had to run programs that move the data; you had to make sure the data got moved correctly; and you had to remap the servers to the new storage. It was difficult.

In the virtualization environment, I can decide to migrate a server from array A to array B, because array A's service contract runs out next month. Depending on how much data there is on that server, a message comes back that says I completed that. [There was] no downtime [and] users didn't notice. My two favorite things about any feature in any computing product: no downtime and users didn't notice.

VSphere 5 enhances this process by using mirror mode to transfer writes that are in process, and mirror mode enhances writes for linked clones. When you run Storage vMotion, the host or whatever is managing that server reads all the data from array A and writes it to array B. If array A and array B are from the same vendor, and both support VAAI, there's a VAAI command to say, "Copy this data from array A to array B." The bad news is that it only comes with the Enterprise or Enterprise Plus licenses for VMware.

Look, in each version of VMware they managed to make this process run substantially faster. Notice the green line that represents ESX 5.0; that's because we're doing some offload with VAAI.

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