If the metadata controller on your SAN fails for any reason, another computer running Xsan can take over. Metadata controller failover is built into Xsan, unlike many SAN solutions that require you to pay extra for this high-availability feature.
Xsan software includes both the metadata controller and file system client components. Using Xsan administration tools, you can specify the laws of succession, or the order in which Xsan metadata controllers take over for a failed controller. Sophisticated algorithms ensure that succession occurs properly, avoiding split brain, or multiple conflicting metadata controllers. Once the file system clients elect a new metadata controller, the failed system can be deactivated until the problem is resolved.
For high-volume, mission-critical production environments, you may want to dedicate a computer as a standby controller. A standby controller also enables you to update Xsan software without interrupting service to your users.