Overcommitted means you have assigned out more, in volume space, than you actually have in physical space in the SAN. This space is thin provisioned so you may not have actually used it yet but you have the potential to run out of physical space in an over committed scenario.
>From the MSA "free space" standpoint, this means how much actual space you have left in the pool. This is what you really want to be concerned about. When this number reaches zero then the array will not except any more writes and you'll be in a world of hurt.
>From a VMWare perspective, it has no idea what you are doing on the back end. Because of the ability to "over commit" you could have provisioned a 16TB datastore with only 5TB of actual space in the SAN. So, if I've used 4TB of that then VMWare will tell you that you have 12TB left and the MSA will say you only have 1TB. The MSA value is what we are more concerned about.
So, add up all your volume sizes from Pool B and see how this differs from the space actually present in the pool. You really don't want to be wildly over committed/provisioned unless you're doing it with a specific purpose in mind and you are going to stay on top of the storage running out on the MSA and purchase additional storage before you actually run out. I prefer to turn over commitment off on the Pools as a safety mechanism but there are some valid reasons for it.
Finally, if you've recently deleted a bunch of stuff from a datastore, VMWare will show that free and the storage might not. This is because a zero reclaim has not occurred. Zero reclaim is handled differently in different versions of VMWare so best to search the VMWare KB's for guidance on your setup (or call VMWare support).
>From the MSA "free space" standpoint, this means how much actual space you have left in the pool. This is what you really want to be concerned about. When this number reaches zero then the array will not except any more writes and you'll be in a world of hurt.
>From a VMWare perspective, it has no idea what you are doing on the back end. Because of the ability to "over commit" you could have provisioned a 16TB datastore with only 5TB of actual space in the SAN. So, if I've used 4TB of that then VMWare will tell you that you have 12TB left and the MSA will say you only have 1TB. The MSA value is what we are more concerned about.
So, add up all your volume sizes from Pool B and see how this differs from the space actually present in the pool. You really don't want to be wildly over committed/provisioned unless you're doing it with a specific purpose in mind and you are going to stay on top of the storage running out on the MSA and purchase additional storage before you actually run out. I prefer to turn over commitment off on the Pools as a safety mechanism but there are some valid reasons for it.
Finally, if you've recently deleted a bunch of stuff from a datastore, VMWare will show that free and the storage might not. This is because a zero reclaim has not occurred. Zero reclaim is handled differently in different versions of VMWare so best to search the VMWare KB's for guidance on your setup (or call VMWare support).