Home > Storage > PowerScale (Isilon) > Product Documentation > Data Protection > Data Protection with Dell PowerScale SnapshotIQ > Data protection with SnapshotIQ
SnapshotIQ can take read-only, point-in-time copies (snapshots) of any directory or subdirectory within OneFS. When a snapshot is taken, it preserves the exact state of a file system at that instant, which can then be accessed later. This immutable, point-in-time copy has various applications. For example, snapshots can be used to make consistent backups, or to restore files which were inadvertently changed or deleted. Snapshots are also for quickly identifying file system changes.
Typically, only a small percentage of the file system changes in a given time, so most storage systems do not keep fully redundant copies. Instead, generally, only the differences from the current file system state are stored.
A OneFS snapshot is basically a logical pointer to data that is stored on a cluster at a particular point in time. Each snapshot references a specific directory under OneFS and includes all the files stored in that directory and its subdirectories. If the data referenced by a snapshot is modified, the snapshot stores a physical copy of the data that was modified. Snapshots are either created according to user configuration or are automatically generated by OneFS to facilitate system operations.
Snapshots can be identified and located either by a unique name or a system-generated snapshot ID. A snapshot name is specified by a user and assigned to the virtual directory which contains the snapshot. A snapshot ID is a numerical identifier that OneFS automatically assigns to a snapshot.
OneFS Snapshots are highly scalable and typically take less than one second to create. They create little performance overhead, regardless of the level of activity of the file system, the size of the file system or the size of the directory being copied. Also, only the changed blocks of a file are stored in a snapshot thereby ensuring highly-efficient storage capacity utilization. User access to the available snapshots is over a special hidden ‘portal’ directory under each file system directory.
SnapshotIQ can also create up to twenty thousand snapshots on a cluster. This large quantity provides a substantial benefit over most other snapshot implementations, because it allows the snapshot intervals to be far shorter, and hence offer more granular recovery point objectives (RPOs).