KERNSAFE - iSCSI SAN Software and Storage Virtualization

Preview of iStorage Server Snapshot Feature

Snapshot is the state of a system at a particular point in time. It refers to an actual copy of the state of a system. Snapshot feature is especially valuable in High-Availability clusters because they cannot bear service stoppages. To avoid downtime, high-availability systems may instead perform the backup on a snapshot—a read-only copy of the data set frozen at a point in time—and allow applications to continue writing to their data. In other words, the time needed to create the snapshot does not increase with the size of the data set, whereas the same for a direct backup is proportional to the size of the data set. In some systems once the initial snapshot is taken of a data set, subsequent snapshots copy the changed data only, and use a system of pointers to reference the initial snapshot. This method of pointer-based snapshots consumes less disk capacity than if the data set was repeatedly cloned.