Volume Manager shows more space available than Dataset

[artis1sysop]

I'm inheriting management of the company's FreeNAS device, and I don't know how the other system admin set this up, but why does my Volume show 983.4 GB available but the Dataset show only 539.2 GB available?

On a side note -- The other system admin named the Volume "BackupFiles" and the Dataset with the same name "BackupFiles". How can I rename these?

 

[danb35]

How can I rename these?

You can't*. As to your question about space, see http://doc.freenas.org/11/storage.html#view-volumes:

Note that in this example, there are two datasets named volume1. The first represents the ZFS pool and its Used and Available entries reflect the total size of the pool, including disk parity. The second represents the implicit or root dataset and its Used and Available entries indicate the amount of disk space available for storage.

* Well, you can, but you'll need to do it from the CLI, and the pool and its root dataset will still have the same names. That is, there will always be two listings with the same name.