Click here for more SAN School lessons. LAN-free backup usually involves the ability to share a SAN connected tape library between all the nodes connected in the SAN. The backup server simply coordinates access to the tape resources. Each server in the SAN actually runs a copy of the backup engine and moves its own data to tape. This is sometimes called the "SSO" or shared storage option from some backup vendors. The backup server becomes the traffic cop for the SAN connected tape resources and allows each server in the SAN to back up its own data. This removes the need to "PULL" data over the LAN via backup agents to a backup server connected tape resource. Serverless backup is accomplished by the backup server having the ability to connect to storage on behalf of other hosts connected to the SAN and back up that host's storage on its behalf. This usually involves the use of snapshot or image copies of the production LUNs in the SAN. The snapshot is used as the source media for backup so that the production application can continue during backup. The snapshot is given access through LUN security in the SAN for access by the backup server,and the backup server sends the data to tape. Another method is to use the SCSI extended copy command called E-Copy which allows even the backup server to get out of the backup path. E-copy allows data to move directly from disk to tape via a "data router" which provides the E-copy intelligence. Chris
The views and opinions expressed by Christopher L. Poelker are his alone and not necessarily shared by Hitachi Data Systems.
This was first published in April 2004