How space management works
The space management capabilities of Data ONTAP allow you to configure your storage systems to provide the storage availability required by the users and applications accessing the system, while using your available storage as effectively as possible.
Data ONTAP enables space management using the following capabilities:
- Space guarantees
- Space reservations
- Fractional reserve
- Automatic free space preservation
- What kind of space management to use
The type of space management you should use depends on many factors, including your tolerance for out-of-space errors, whether you plan to overcommit your aggregates, and your rate of data overwrite.
- What space guarantees are
Space guarantees on a FlexVol volume ensure that writes to a specified FlexVol volume or writes to files with space reservations enabled do not fail because of lack of available space in the containing aggregate.
- What space reservation is
When space reservation is enabled for one or more files or LUNs, Data ONTAP reserves enough space in the volume (traditional or FlexVol) so that writes to those files or LUNs do not fail because of a lack of disk space.
- How Data ONTAP can automatically provide more free space for full volumes
Data ONTAP can automatically make more free space available for a FlexVol volume when that volume is nearly full. You can choose to make the space available by first allowing the volume size to increase, or by first deleting Snapshot copies.
- How aggregate overcommitment works
Using aggregate overcommitment, the storage administrator can appear to provide more storage than is actually available from a given aggregate, as long as not all of that storage is currently being used. Aggregate commitment is also called thin provisioning.