In a Filer-to-Filer or 3-way backup model, the NVBU Server instructs Filer A to start backing up data to the tape device attached to Filer B. Backups and restores for Filer B are performed directly, while backups and restores for Filer A are routed through the network. The backup index information is transferred from Filer A to Server over the LAN via NDMP. This model allows sharing of tape libraries among multiple filers.
The advantages are that the NDMP backup of filer A, in the scenario described, is allowed to transfer data directly between the filer A and filer B without traveling over the network back to the NetVault server. This reduces load on the NetVault server and network traffic.
One of the few discovered disadvantages is a slightly increased load on filer B while it is transferring data from filer A to the tape drive. This is by no means an issue.
How to configure Filers for 3-way Backups:
First, you add both filers to the NDMP plugin.
In Device Management, you add the library to the filer that it will be connected to.
After that, the process is the same as setting up a regular backup; simply set up the backup of the filer that is NOT connected to the library and on the target tab of the job, switch the radio button to 'Specify device.' The library attached to the other filer will be there. Select it, making sure nothing else is selected.
Additionally, you can target that library for a file system backup on other servers, if necessary.
