In NetBackup Advanced Client, one of two types of supported snapshots. Unlike a mirror, a copy-on-write does not create a separate copy of the client’s data. It creates a block-by-block "account" that describes which blocks in the client data changed and which have not from the instant the copy-on-write was activated. This account is used by the backup application to create the backup copy.
A technique for preserving the original data. Before data is modified by a write operation, the original copy of data is copied to a different location.
A technique for preserving the original of some data. As data is modified by a write operation, the original copy of data is copied.
Applicable to Storage Checkpoint technology, where original data, at the time of the Storage Checkpoint, must be copied from the file system to the Storage Checkpoint when it is to be overwritten. This preserves the frozen image of the file system in the Storage Checkpoint.