Specifies the percentage of disk space that only Snapshot copies can use. The storage system cannot use the reserved space for the active file system.
The default value for this field is 20 percent.
Using the Snapshot copy reserve offers this advantage: If the active file system is at 100 percent, deleting files from the active file system frees disk space because the deletion causes additional disk space to be consumed only in the disk space reserved for Snapshot copies. If you do not have a Snapshot copy reserve, deleting files in the active file system does not free disk space because after the deletion, the amount of disk space that was used by these files is consumed by the Snapshot copy.
Note: If Snapshot copies use all the Snapshot copy reserve at the time when the active file system is full, you cannot free disk space by deleting files from the active file system. That is because the same disk space used by the deleted files is to be used by Snapshot copies. In this situation, you cannot create new files in the active file system until you free disk space by deleting Snapshot copies.