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How Data ONTAP uses deleted active file disk space

When enough disk space is available for Snapshot copies in the Snapshot copy reserve, deleting files in the active file system frees disk space for new files, while the Snapshot copies that reference those files consume only the space in the Snapshot copy reserve.

If Data ONTAP created a Snapshot copy when the disks were full, deleting files from the active file system does not create any free space because everything in the active file system is also referenced by the newly created Snapshot copy. Data ONTAP has to delete the Snapshot copy before it can create any new files.

The following example shows how disk space being freed by deleting files in the active file system ends up in the Snapshot copy:

If Data ONTAP creates a Snapshot copy when the active file system is full and there is still space remaining in the Snapshot reserve, the output from the df command—which displays statistics about the amount of disk space on a volume—is as follows:

Filesystem                 kbytes    used    avail  capacity  Mounted on     Vserver
/vol/vol0/                3000000 3000000        0      100%  --             vs1
/vol/vol0/.snapshot       1000000  500000   500000       50%  --             vs1

If you delete 100,000 KB (0.1 GB) of files, the disk space used by these files is no longer part of the active file system, so the space is reassigned to the Snapshot copies instead.

Data ONTAP reassigns 100,000 KB (0.1 GB) of space from the active file system to the Snapshot reserve. Because there was reserve space for Snapshot copies, deleting files from the active file system freed space for new files. If you enter the df command again, the output is as follows:

Filesystem  	              kbytes     used     avail  capacity  Mounted on     Vserver
/vol/vol0/                3000000  2900000    100000       97%  --             vs1
/vol/vol0/.snapshot       1000000   600000    400000       60%  --             vs1