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.

• 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, Data ONTAP reserves enough space in the volume (traditional or FlexVol) so that writes to those files do not fail because of a lack of disk space.
• What fractional reserve is
  If you have enabled space reservation for files or LUNs, you can reduce the size of the reserved space by using fractional reserve. You set fractional reserve using the vol options command.
• How space reservation and fractional reserve settings persist
  Space reservation and fractional reserve settings persist across reboots, takeovers, givebacks, and SnapRestore operations, provided there is enough space in the volume.
• 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.
• Space reservation and fractional reserve examples
  These examples demonstrate how setting space reservations and fractional reserve affects available space.
• Estimating how large a volume needs to be
  Before you create a volume, you can estimate how large it needs to be. The method you use to estimate the volume size depends on whether you need to create Snapshot copies of the volume.