Efficient file recovery with Snapshot copies
Snapshot copies consume minimal storage space because only changes to the active file systems are written. You can back up your volumes more frequently.
A Snapshot copy is a read-only image of a traditional volume, a FlexVol volume, or an aggregate that captures the state of the file system at a point in time. Two Snapshot copies created in sequence differ only by the blocks added or changed in the time interval between the two. This block incremental behavior limits the consumption of associated storage capacity.
When a Snapshot copy is created, the data is not copied from one location to another. As a result, you can store up to 255 Snapshot copies at one time on each volume without any performance overhead.
Data ONTAP provides a default Snapshot copy schedule for each volume. You can configure the schedule to fit your needs. This schedule creates Snapshot copies automatically and deletes old Snapshot copies after a predetermined amount of time.
For more information about Snapshot copies, see the Data ONTAP Data Protection Online Backup and Recovery Guide.
- What Snapshot disk consumption is
Data ONTAP preserves pointers to all the disk blocks currently in use at the time the Snapshot copy is created. When a file is changed, the Snapshot copy still points to the disk blocks where the file existed before it was modified, and changes are written to new disk blocks.
- How Snapshot copies consume disk space
Snapshot copies minimize disk consumption by preserving individual blocks rather than whole files. Snapshot copies begin to consume extra space only when files in the active file system are changed or deleted. When this happens, the original file blocks are still preserved as part of one or more Snapshot copies.
- What the Snapshot copy reserve is
The Snapshot copy reserve sets a specific percent of disk space for Snapshot copies. By default, the Snapshot copy reserve is 20 percent of disk space. The Snapshot copy reserve can be used only by Snapshot copies, not by the active file system.
- What file folding means and how it saves disk space
File folding describes the process of checking the data in the most recent Snapshot copy, and if this data is identical to the Snapshot copy currently being created, by referencing the previous Snapshot copy instead of taking up disk space writing the same data in the new Snapshot copy.