Posted by: Raj Perumal
FC, iSCSI, SAN, thin disks, thin provisioned, thin provisioning, Virtualization, VMWare, vSphere
Hi folks, so with all this talk of storage it’s about time I spoke a little bit about thin provisioning! Now here is a new question I’ve been asked a lot. What exactly is thin provisioning?
Well you might see this term thrown about not just with VMware but with SANs as well. In the simplest of terms, thin provisioning is the act of over-allocating storage. Thin provisioning is a feature provided for you in VMware but it is also provided in many SAN products natively.
Here is an example. Let’s say you have 1 TB of space left on your SAN and you get a few customer requests for allocating some new virtual servers in the environment. The total sum of all the disks you need might exceed the 1 TB you have left. How do you deal with this? When you create the disks, you create them as “thin” instead of “thick”. So let’s say you need to create a 500 GB data drive. But you know that the customer will not use up that whole 500 GB drive for at least a year. All you have to do is create the drive as thin and then the drive will only actually use up the space that is actually used instead of the whole 500 GB. So if there is 50 GB’s of data on the drive, that is the actual size of the disk. This way you have plenty of time to go out and shop around to get the storage you want down the road. You don’t need it up front.
What are the disadvantages? If you forget to add more disk before you run out of storage then you can end up crashing your environment. Not good! Also with thin provisioning you can run into performance issues. I tend to reserve thin provisioning for non-critical items in my environment.