The Symantec Backup Exec for Windows Servers SAN Shared Storage Option enables multiple media servers to share secondary storage devices, such as robotic libraries, in a SAN. The secondary storage devices are not directly connected to a single server by SCSI, but are connected to a Fibre Channel Switched Fabric (FC-SW) or iSCSI.
To allow for sharing of storage devices and media between multiple media servers, a shared Advanced Device and Media Management (ADAMM) database resides on one media server called the database server or primary server. All media servers on the SAN connect to this database to obtain a single, unified view of all shared devices and media. Backup Exec uses this shared database to arbitrate all device and media requests with comprehensive overwrite protection policies to prevent accidental media overwrites. To resolve potential access conflicts between multiple media servers, Backup Exec "reserves" robotic arms and tape devices while operations are being performed.
Media catalogs are shared between media servers, so restore operations can be performed using any media servers that share catalogs. If the media must be moved from one device to another on the SAN, the media does not have to be cataloged again. In a shared storage environment, secondary storage devices also can be attached to the local SCSI, SATA, SAS, USB, or ATAPI buses of any media server. However, these local devices, disk or tape drives connected to a server, are only available to the server to which they are attached. Storage devices used with the SAN Shared Storage Option must have a vendor-assigned serial number.
In the following example of a shared storage environment, the database server and the media servers transmit data over the FC-SW through a fibre to SCSI bridge (router) to secondary storage devices (SCSI robotic libraries).
If you have multiple SANs, it is recommended that you treat each SAN independently, with each SAN having its own Backup Exec database server for the shared ADAMM database and catalogs for that loop. Using a single Backup Exec database server for more than one SAN increases the number of single-point failures that can affect the system.