Choosing the best way to archive

Although all the data required to create an archive is on the storage system, it is not necessarily efficient to back up both of the required archive components using the same backup method. Figuring out exactly how best to tackle the task of archiving depends on the specific environment.

The LUN object that you want to archive is captured in a Snapshot copy located on the storage system. The object can be backed up directly from the storage system using the storage system's dump command, backed up directly from the storage system using the NDMP protocol, or even copied out to a NearStore® storage system.

When backing up the specific SnapInfo subdirectory that corresponds to the desired full database backup set, the required data is actually in the active file system of a mounted LUN (which is in the storage system's active file system). There are two ways to back up this particular information.

Using a Windows based backup application, such as the NTBackup utility that ships with Windows, back up the specific directory to a tape device or to a file on a NearStore storage system, for example. Neither an NDMP-based backup or the storage system's dump command can back up this data from the SQL Server's active file system.

Another, and much less efficient, method to back up the SnapInfo information is to back up the entire LUN object as captured in a Snapshot copy on the storage system. Doing this is very similar to the method used to back up the LUN object containing the database files. The disadvantage to backing up the LUN object for the SnapInfo directory is that the backup size is that of the entire LUN object itself (the entire LUN--no matter how much or how little data is contained within).

It is important to back up a LUN object that is in a Snapshot copy created by SnapManager. Because LUNs from multiple hosts can be stored on the same storage system volume, only LUNs that belong to the host that created the SnapManager Snapshot copy are consistent. All LUNs within the Snapshot copy that belong to other hosts are not consistent.