A down server is detected within 30 seconds, but can be configured for any time threshold. Windows operating system updates or other maintenance that cause a reboot may be reason to increase this threshold to several minutes. Failover will transfer all the camera processes from running on the down server to running on a redundant server. It will transfer only cameras that are Movable according to the camera configuration as defined in the Device settings. Some devices are not movable by nature (USB devices, or analog cameras plugged into a video card on the down server for example). When a down server comes back up, and its cameras have been failed over to another server, it will now be considered a redundant server, since it has no cameras.
Failover works if you are using a file storage device (for example, NAS) instead of block storage (such as SAN or a local disk) because the pool of storage does not follow the camera when it is moved. If you have central storage (with a NAS), the storage is always accessible from any server. If your storage system is a SAN, Symphony can be configured to copy data to a camera's primary server when it is manually swapped back after a failover occurs. For details, see Customizing Storage Settings. |