Backup Architecture: SAN, LAN (NBD), and HotAdd

Backup over a SAN or VMware HotAdd is recommended for superior performance. SAN has significant advantages over LAN (NBD):

• Impact on ESX server processing is reduced. On a LAN, the ESX server needs to read VMDKs and transfer them to the proxy server. On a SAN, the proxy servers read directly from storage, bypassing ESX servers.

• Network contention is reduced.

• Network transmission time is reduced.

• Fewer connections are required on the vSphere server.

For many small- to medium-sized companies, LANs are cost effective. In such environments, Agentless VMware Backup can be easily deployed for LAN backup, though performance is constrained by the LAN.

For HotAdd transport mode, vStorage APIs use the SCSI hotadd functionality of the ESXi host to mount a virtual machine’s associated virtual disks to backup storage, such as the Catalogic vStor server, for backup jobs. Using HotAdd requires that SCSI disks be used.