Data ONTAP maintains a configurable Snapshot schedule that creates and deletes Snapshot copies automatically for each volume. You can also create and delete Snapshot copies, and manage Snapshot schedules based on your requirements.
What a Snapshot copy is A Snapshot copy is a read-only image of a traditional or FlexVol volume, or an aggregate, that captures the state of the file system at a point in time. Data ONTAP maintains a configurable Snapshot copy schedule that creates and deletes Snapshot copies automatically for each volume. You can also create and delete Snapshot copies manually.
User access to Snapshot copies
By default, every volume contains a directory named .snapshot through which users can access old versions of files in that directory. Users can gain access to Snapshot copies depending on the file-sharing protocol used—NFS or CIFS. Access to Snapshot copies can be turned off.
How Data ONTAP Snapshot copies work in an iSCSI or FC network
If you take a Snapshot copy of a file system when an application is running, the Snapshot copy might contain inconsistent data. You can take measures (such as quiescing the application) to ensure that the data is consistent before you take the Snapshot copy.
Restoring files from Snapshot copies You might have to restore a file from a Snapshot copy if the file was accidentally erased or corrupted. You can use the SnapRestore feature to automatically restore files or volumes from Snapshot copies.
Creation of Snapshot copy schedules Data ONTAP provides a default Snapshot copy schedule for each FlexVol volume. You can configure the schedule to fit your needs. The schedule creates Snapshot copies automatically, and deletes older Snapshot copies after a specified period.
Creating Snapshot copies manually
You might need to create Snapshot copies outside a specified schedule. You can create Snapshot copies manually by using the snap create command.
Why you might need to access a particular Snapshot copy
You might need to access an earlier version of a file, because a file was changed, corrupted, or erased. You might notice the issue only after one or more Snapshot copies were created with the incorrect copy of the file. When looking for the version of the file you need, you should look for it by means of the creation time of the Snapshot copy.
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.
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.
Displaying the rate of change between Snapshot copies
You can use the snap delta command to view the rate of change between two Snapshot copies as well as the rate of change between a Snapshot copy and the active file system. This information can help you determine a suitable Snapshot copy schedule and Snapshot copy reserve.
Deleting Snapshot copies automatically You can define and enable a policy for automatically deleting Snapshot copies by using the snap autodelete command. Automatically deleting Snapshot copies can help you manage space utilization.
Displaying space reclaimed from deleted Snapshot copies
You can display the amount of space you can reclaim by deleting one or more Snapshot copies in a volume by using the snap reclaimable command. The amount of space displayed is an approximation because writing to the volume, creating Snapshot copies, or deleting Snapshot copies causes the reclaimed amount to change.
Renaming Snapshot copies
You might want to rename a Snapshot copy generated by the snap sched command if it contains data that you want to save. The snap sched command overwrites and deletes regularly scheduled Snapshot copies. You can use the snap rename command to save a Snapshot copy.
Volume move and snap commands
During the volume move cutover phase, the SnapMirror source volume is not accessible. Therefore, the snap commands do not work.