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The words and concepts of vME that you'll encounter are defined and introduced in this section.


A dataset is a generic name of vME components: pool, source, snapshot, and clone. It is the layer where data can be stored and retrieved.


The pool is a combined of disk drives. A pool can be have one or more sources. Sources created within the pool see all the pool's capacity and can grow up to the available space for the whole pool. Any one source can take all the available space, making it impossible for other source in the same pool to grow and contain new data. One of the ways to deal with this is to use space reservations and quotas.


A source is created in the boundaries of a pool. A source file can only belong to one pool, but pool can contain more than one source file. Source can have reservations (minimum guaranteed capacity), quotas, compression, and many other properties. Sources can be nested, meaning you can create one source in another. Unless you specify otherwise, sources will be automatically mounted within their parent. The uppermost source is named the same as the pool and automatically mounted under the root directory, unless specified otherwise.


Snapshots are point-in-time snaps of the source's state. Creating a snapshot means recording source vnodes and keeping track of them. Once the data on that inode is updated, the old block of data is retained. You can access the old data view by using said snapshot, and only use as much space as has been changed between the snapshot time and the current time.


Snapshots are read-only. If you want to mount a snapshot and make changes to it, you'll need a read-write snapshot, or clone. Clones have many uses, one of greatest being boot environment clones...

Data Container

A dataset is a container mounted at some sources.