VMWare ESX Storage VMotion (svmotion)
In a different write-up about VMWare ESX 3.5 I complained about how badly Storage VMotion was implemented. I wanted to come back to that topic though since even though VMWare failed badly providing an easy way to do it, the functionality itself is pretty cool. What is Storage VMotion? Storage VMotion or SVMotion is the feature inside ESX 3.5 that allows you to move a machine (VM) from one storage location to another without interruption of service. If that does not tell you anything, see it like pulling a hard drive out of a server and putting it into another server 3 racks down in your data center and at the same time that is still up and running.
I did not want to put up with the lousy implementation of Storage VMotion and searched around. I found several GUI tools (all unsupported by VMWare) that promised to take the pain out of Storage VMotion. I have tested them all and found some worked great, while others did not. The best and most reliable implementation (in my opinion) comes from Lostcreations.com/viplugins.com. This GUI tool uses the plugin feature of Virtualcenter 2.5 and adds an easy way to migrate the storage from one storage location to another right from the VCC (VirtualCenter Client). Once installed and enabled, you just select a VM, right click on it and select "migrate storage". A new window opens up and allows you to drag and drop the machine and the virtual hard drive(s) onto a new storage location. You can see disk size, free space and a few other helpful things. Once satisfied you commit the change and the Virtual Machine starts moving using Storage VMotion.
How does this benefit you (be it a web host or not)? Let’s assume the phyiscal host server running ESX is ready for retirement. If the VM is sitting on local storage you would have to power down the VM and cold migrate it to a new server, SAN, or attached storage of any kind. This could mean a long downtime for a VM. Now you can move the VM in the middle of the day with no interruption for the customer. The performance will suffer a little bit, but overall the VM will maintain high uptime. Another example: Your leased SAN comes off lease and you need to replace it. Instead of a) incurring downtime and b) spending a fortune on EMC SAN Copy you can now easily move your VMs to the new SAN with no interruption in servive. For a web hosting business trying to maintain a near 100% uptime this is huge.
Conclusion: Storage VMotion is a great feature, but currently badly implemented by VMWare. Some 3rd party developers stepped up to the plate and now this feature is kicking butt. I have moved over 80 VMs already using Storage VMotion with 100% uptime.