Topics | Snapshot Engines | Support | Related Topics
The system supports both software-based and hardware-based snapshots. A software-based snapshot is essentially an instantaneous set of pointers to the original data (sometimes referred to as a logical view) as it was at a given point-in-time. When the original data is changed, the pointers will trigger a copy of the original data block; this maintains the snapshot, allowing data protection operations to proceed without interruption from I/O.
Hardware-based snapshot implementations differ between vendors, but the principle is the same. Copy operations occur within the hardware snapshot provider's disk arrays. Because of the speed of hardware copies, some hardware snapshots are full, point-in-time copies of the data. Depending on the vendor's implementation, pointers (logical views) may be used, but they are controlled by the vendor's hardware and/or drivers. This offloads work from the production server to the vendor's hardware. Furthermore, hardware snapshot providers often include additional functionality, such as disk mirroring and cloning.
In addition to providing the basis for a consistent backup or QR Volume, in some cases snapshots can be created, mounted, unmounted, and deleted as separate entities. When a snapshot is mounted, it looks like the volume at the point-in-time of snapshot creation. In the case of VSS, mounting a snapshot on a different client is referred to as transporting the snapshot, or shadow.
Hardware snapshots are created at the LUN level, not the partition level. It is recommended that each LUN have only one partition. Using LUNs with multiple partitions may cause unexpected results.
The Quick Recovery Agent provides the option of creating a snapshot independently of QR Volume Creation (i.e., the snapshot can be manipulated as an independent entity). Through the QR Volume Browse window, you can mount, unmount, and delete snapshots created in this manner. There may be some limitations depending upon which snapshot engine was used to create the snapshot. See the descriptions of the snapshot environments for more details.
Snapshots can also be created using the utilities that accompany your hardware providers, but these snapshots will not be accessible from the QR Volume Browse window.
For ContinuousDataReplicator (CDR), specify the following snap engines:
For Windows 2003 or higher, VSS is used as the default snap engine.
For Windows 2000, Qsnap is used as the default snap engine.
Snapshots can be deleted from the Browse QR Volumes window or in Volume Explorer. Deleting snapshots in this manner will remove them from the CommServe database, but the snapshot may still remain on the hardware provider and require manual deletion using the provider's utility software.
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Select Hide Source Snapshot in the Browse QR Volumes dialog, if you want to hide from view the source snapshots created by ONTAP SnapVault or QSnap. |
Agents support different snapshot environments; see Support Information - Snapshot Engines for a complete list of products and the snapshot engines they support. The following overviews provide instructions on configuring and working with each snapshot environment.
EMC
HP/Compaq
Hitachi
NetApp
Generic Enablers — a standard feature of the Quick Recovery Agent — allow you to support other hardware snapshots for the Quick Recovery Agent, using snapshot scripts that you provide based using standard templates. These scripts will initialize the hardware snapshot (or clone), manage the Business Continuance Volume (BCV) pair for data protection operations, and handle the mounting and unmounting of volumes.
To perform a data protection operation using this Agent a specific Product License must be available in the CommServe® Server.
Review general license requirements included in License Administration. Also, View All Licenses provides step-by-step instructions on how to view the license information.
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