Using NetBackup for SQL Server with Snapshot Client NetBackup Snapshot Client for SQL Server overview
and restoring standard SQL Server database images or images taken from snapshots. However, there are fundamental differences in the technologies.
Snapshot Client backups, in contrast to standard backups, are file-based. This means that NetBackup determines the file list constituting the SQL Server object and backs it up asynchronously with respect to SQL Server. On the other hand, standard backups are stream-based, which means that SQL Server provides data to NetBackup buffer-by-buffer constituting a backup stream. The key role of SQL Server in file-based backups is to provide the mechanism for freezing database activity long enough for NetBackup to invoke a so-called snapshot provider that creates volume snapshots of the files.
The snapshot method is the software/hardware component that creates the snapshot image of the files. The method may be a Symantec product such as Volume Manager, an operating system component such as VSS (Microsoft Virtual Shadow Service), or a third-party product. Snapshot methods use a variety of technologies such as copy-on-write, split-mirror, or RAID. They also provide several competing methodologies that may have different consequences in respect to factors such as recovery speed, impact of the backup on the client processor, and cost of specialized disks or processing units.
Snapshot Client features
The following NetBackup Snapshot Client features are available for use with NetBackup for SQL Server:
A snapshot is a disk image of the client's data made almost instantaneously. NetBackup backs up the data from the snapshot image, not directly from the client’s primary data.
Instant Recovery (Persistent Frozen Image or PFI)
An instant recovery backup is similar to a snapshot backup except that the snapshot is not transferred to tape. The restore may be made directly from snapshot copy.
Persistent Frozen Image with Backup to Tape
This feature is similar to the Instant recovery feature except that a backup copy is made to a tape storage unit. If the image is needed for a restore, then a disk copy will be used unless it has been swapped out due to storage contention. In this case, the restore will fall back to the tape copy of the backup.
Off-host alternate client backup
An off-host alternate client backup shifts the burden of backup processing to an alternate client, reducing the impact on the client's computing resources ordinarily caused by a local backup. The backup agent reads the data from the shared disk and writes it to storage.