Some backup basics

Incremental: Backs up only data that has changed since the last backup. The least amount of data is backed up with this method, shortening backup windows. This is a quick method that skips any file that has the same date as the same file within the backup archives.
Differential: Back up of all files changed since the last full backup. Upon restore, the full and last differential backup medium will be used. A negative about this method is that throughout the week, the backup will become larger until the next full backup. This can impinge on the backup windows.
CDP – Continuous Data Protection: This is like a snapshot backup – a pint-in-time snapshot of a file system. Oracle has it: RMAN and Flashback – a database snapshot utility that is a set of SQL commands that lets users view data as it existed at various points in time. This enables one to identify points of corruption and to restore a database to a point before the corruption” (Storage Magazine, 2005). IBM Tivoli has it: the client software has the option of point-in-time restore. EMC’s Celerra NAS appliance has the checkpoint utility which takes a complete snapshot of a file system in seconds. NDMP is often used to back up the Celerra NAS checkpoints:
NDMP: Network Data Management Protocol is a popular way to backup immense data on NAS devices. Often a fast LAN-free method, NDMP is efficient in the way data is transferred from the NAS directly to the backup server without any third-party backup client software installed on the NAS device. Using a LAN-free NDMP backup, the LAN is free of traffic from the large NAS backup because NDMP directly accesses the backup server often through SCSI or fiber medium, bypassing the rest of the LAN that contains the other server nodes.
VTL: The latest backup medium, the Virtual Tape Library, is a disk library dedicated to backup data storage. Disk is faster than tape and this method shortens backup windows considerably on a fast fiber-based SAN. The backup database is then dumped to tape periodically and the tape is then transferred to offsite vaulting for DR.

References:
Storage Magazine. (2005). CDP poised to replace traditional backup methods. SearchStorage.com. Retrieved June 3, 2009 from http://searchstorage.techtarget.com/magazineFeature/0,296894,sid5_gci1257934,00.html

About Steve J
M.A. Information Systems

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