v101 – Data Migration (or “Avoiding all night progress bar parties”)

(This post is part of a series on “Virtualization 101” — see the first post for an overall explanation of my approach in this series.)


Quick! Who out there loves watching progress bars? I mean, who just thinks “man, what I want to do on a Friday night is watch a progress bar with semi-accurate time to completion estimates”? After all, if it runs long enough, you can go to IHOP/McDonald’s/etc. on Saturday morning after staying up all night and then go back to work!

Yeah….me too.

This topic as well takes me back to the beginning of virtualization in my career. Server hardware refreshes were what triggered the need to migrate data…but the most tedious part about refreshing physical servers was moving all their data around (especially for file servers with hundreds of gigabytes to terabytes of data).

As we discussed earlier, server virtualization removes the need to reinstall/migrate OSes. But still, what about the data? After a certain point, you still need to move data around, right?

When using VMware vSphere, we have a fantastic capability called Storage vMotion. Once you have a virtual server, you now have an incredible amount of extra capabilities due to the additional layer of abstraction between the server OS (i.e. Windows, Linux, Netware, etc.) and the hardware, i.e. the physical disks in this case. What VMware provides is the ability to define multiple datastores (i.e. that point to local disk on your server or a storage array) and seamless migrate the data disks for your virtual servers between datastores.

Let me repeat — you can actually take a server’s underlying virtual disks (aka C drive, D drive, /root, /var, etc.) and with about 10 clicks in the vCenter client migrate the actual data (10 GB, 100 GB, 500 GB) between different storage arrays or sets of disks….with ZERO downtime. This is something akin to magic in the IT world. See this video for a walkthrough detailing Storage vMotion in vSphere 4.

As well, for some additional perspective Varrow’s own Jason Nash has a Storage vMotion walkthrough on a previous version of VMware.

Finally, see this video from a VMware engineer discussing Storage vMotion and its impact on business.

So what’s the impact here?

  • Running out of space on a datastore? No big deal — Storage vMotion your VMs to a different datastore (caveat: don’t get to 100% space utilization…bad things happen then).
  • New storage array coming in the door? No big deal — Storage vMotion your VMs.
  • Need to move VM’s around on your storage array for performance reasons? No big deal — Storage vMotion your VMs.

Fewer downtime windows usually = happier business people and happier IT people too….a rare naturally occuring case of IT and Business alignment.

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