About using thin provisioning with Infinite Volumes

Using thin provisioning with Infinite Volumes offers many advantages over thick provisioning, including the ability to provide more storage to users than is actually available. Before using thin provisioning, you should understand the disadvantages of using thin provisioning and the amount of space that it makes available.

With thin provisioning, the size of an Infinite Volume is not limited by the size of its associated aggregates. You can create a large volume on a small amount storage, adding disks only as they are required. For example, you can create a 10-TB volume using aggregates with 5 TB of storage. The storage provided by the aggregates is used only as data is written. Thin provisioning is also called aggregate overcommitment.

Advantages of thin provisioning

Using thin provisioning with Infinite Volumes provides the following advantages:

•	Defers physical storage costs until the storage is actually required

Users receive the space allocation that they expect, and valuable resources do not remain unused.

•	Facilitates monitoring of aggregate usage

When you use thin provisioning, information about aggregate usage—for example, the Used Size, Used Percentage, and Available Size—reflects the actual space used to store data. When you use thick provisioning, aggregate usage information reflects the allocated space, which typically differs from the space that is actually used to store data.

•	Reduces the need to change the volume size after adding storage

You can configure a thin-provisioned volume to automatically secure more space from its aggregate when it needs to. However, if you have overcommitted your aggregate, you must monitor your available space and add storage to the aggregate as needed to avoid write errors due to insufficient space.

Disadvantages of thin provisioning

Thin provisioning includes the following disadvantages:

•	When any of the aggregates associated with the Infinite Volume are overcommitted, writes to the volume might fail if the volume lacks sufficient space to accommodate the incoming data.

•	Administrators must actively monitor available space on the aggregates associated with the volume, and add more physical storage when required.

Space usage that is not affected by thin provisioning

When an Infinite Volume uses thin provisioning, not all unused space is available for data. The storage system itself requires space for the following:

•	For the namespace constituent, which always uses thick provisioning

For example, if you create a new Infinite Volume with a 2-TB namespace constituent and use thin provisioning, the Infinite Volume appears to use 2 TB of space even if it does not contain any data. The size of the namespace depends on several factors, including the configured size of the Infinite Volume.

•	For the metadata that each data constituent requires

For an Infinite Volume, the total space required for data-constituent metadata is approximately 0.5 percent of the configured size of the Infinite Volume.