VMware – Storage Migration (part 2)

Monday, 8. June 2009

In a previous post, I described a VMware Storage Migration task I was assigned and a quick run-down of the capability of the Storage VMotion feature.  Now, I’ll go into more detail about an awesome little tool that could make the process much easier.

The tool is called ‘SVMotion‘ and it is a plug-in to the Virtual Infrastructure client that you may already be using to administer your hosts and guest machines.  Once installed, it adds the ‘Migrate Storage’ option to the right-click menu of your VM’s.  When you select it, you will be presented with a window showing a list of datastores and the ones that the VM and its disks are on.

From here, you can drag the VM and its disks from their source datastore to the destination datastore.  Once you click ok, you’ll see a new ‘Relocate Virtual Machine Storage’ task that will show the migrations progress.

There’s a couple things I’ve learned from my use of this plug-in:

     1.  You have the move the actual virtual machine files as part of the migration whether you want to or not.  This is a Storage VMotion requirement.  If you like where the virtual machine files reside, move them with the disk and then move them back after.

     2.  This item appears to be a quirk of the plugin.  Say you have a VM with multiple disks but only want to move the virtual machine files and the first disk.  When you drag the VM to the destination datastore and click ok (having left the remaining disks in their original location), the plug-in attempts to move all VM files to the destination.  If you have the space, it will begin; if you dont, it will immediately return an error.

Overall, this plug-in is very nice and the price is right (free!).  It’s certainly much more convenient to use the GUI to initiate the Storage VMotion whenever you can.

VMware – Storage Migration (part 1)

Monday, 1. June 2009

Recently, I was tasked with migrating our entire VMware implementation to a new storage array.  Essentially, we are replacing our current SAN with one that is claimed to be bigger, better, and faster.

That sounds great, but how do you move 35 TB of data belonging to 800 VM’s with a minimal impact?  Storage VMotion may be what you’re looking for.

Storage VMotion can be a really useful tool.  Essentially, it can let you move a VM from one datastore to another while the VM is powered on, much like how a standard VMotion can let you live-migrate between hosts.

There are several considerations to keep in mind when preparing for a Storage VMotion.  A more complete list can be found here, but the more common ones we ran into were:

     –  Virtual machines with snapshots cannot be migrated using Storage VMotion.
     –  Virtual machine disks must be in persistent mode or be raw device maps.

The first one should be fairly obvious: you must delete any snapshots before performing an online Storage VMotion.

The second has to do with the disk “mode”.  You can research more about the different mode options but essentially the virtual disk must be able to be snapshotted (i.e. not “independent”) and the changes must be persistent (i.e. not discarded when the VM is powered off or a snapshot is deleted).  This is a requirement as the snapshot functionality is used by the Storage VMotion process.  If you have disks that may be marked as independent, you can plan to power down the machine and change this setting for the duration of the migration, or just migrate it while its off.

There are few different ways to perform a Storage VMotion which I’ll describe in a future post.