HP D2D4009fc HP StoreOnce Backup System Concepts and Configuration Guidelines - Page 78
StoreOnce VTL and NAS replication overview, Replication usage models (VTL and NAS)
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StoreOnce VTL and NAS replication overview The StoreOnce Backup system utilizes a propriety protocol for replication traffic over the Ethernet ports; this protocol is optimized for deduplication-enabled replication traffic. An item (VTL Cartridge or NAS file) will be marked ready for replication as soon as it is closed (or the VTL cartridge returned to its slot). Replication works in a "round robin" process through the libraries and shares on a StoreOnce Backup system; when it gets to an item that is ready for replication it will start a replication job for that item assuming there is not already the maximum number of replication jobs underway. Replication will first exchange metadata information between source and target to identify the blocks of deduplicated data that are different; it will then synchronize the changes between the two appliances by transferring the changed blocks or marking blocks for removal at the target appliance. Replication does trigger housekeeping on the Target Appliance. Replication will not prevent backup or restore operations from taking place. If an item is re-opened for further backups or restore, then replication of that item will be paused to be resumed later or cancelled if the item is changed. Replication can also be configured to occur at specific times (via configurable blackout windows) in order to optimize bandwidth usage and not affect other applications that might be sharing the same WAN link. VTL and NAS replication is configured between devices using "Mappings" and is not known to the backup software but is controlled entirely by the StoreOnce appliance. Catalyst Copy is controlled entirely by the backup software and has no Mappings within the device to configure. A data import process is necessary to recover data from a target NAS or VTL device, But with Catalyst no backup application import is required because the additional copies are already known to the backup software and do not need to be imported. Replication usage models (VTL and NAS) There are four main usage models for replication using StoreOnce VTL and NAS devices shown below. • Active/Passive - A StoreOnce system at an alternate site is dedicated solely as a target for replication from a StoreOnce system at a primary location. • Active/Active - Both StoreOnce systems are backing up local data as well as receiving replicated data from each other. • Many-to-One - A target StoreOnce system at a data center is receiving replicated data from many other StoreOnce systems at other locations. • N-Way - A collection of StoreOnce systems on several sites are acting as replication targets for other sites. The usage model employed will have some bearing on the best practices that can be employed to provide best performance. The following diagrams show the usage models using VTL device types. 78 Replication