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A cold standby failover recording server takes over for the recording server that has become
unavailable after five seconds plus the time it takes for the failover recording server's Recording Server
service to start and the time it takes to connect to the cameras. In contrast, a hot standby failover
recording server takes over faster because the Recording Server service is already running with the
correct configuration and only has to start its cameras to deliver feeds. During the startup period, you
can neither store recordings nor view live video from affected cameras
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When a recording server becomes available again, it automatically takes over from the failover
recording server. Recordings stored by the failover recording server are automatically merged into the
standard recording server's databases. The time it takes to merge, depends on the amount of
recordings, network capacity and more. During the merging process, you cannot browse recordings
from the period during which the failover recording server took over
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If a failover recording server must take over from another recording server during the merging process
in a cold standby failover recording server setup, it postpones the merging process with recording
server A, and takes over from recording server B. When recording server B becomes available again,
the failover recording server takes up the merging process and allows both recording server A and
recording server B to merge back recordings simultaneously.
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In a hot standby setup, a hot standby server cannot take over for an additional recording server
because it can only be hot standby for a single recording server. But if that recording server fails again,
the hot standby takes over again and keeps the recordings from the previous period. The recording
server keeps recordings until they are merged back to the primary recorder or until the failover
recording server runs out of disk space
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A failover solution does not provide complete redundancy. It can only serve as a reliable way of
minimizing the downtime. If a recording server becomes available again, the Failover Server service
makes sure that the recording server is ready to store recordings again. Only then is the responsibility
for storing recordings handed back to the standard recording server. So, a loss of recordings at this
stage of the process is very unlikely
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Client users hardly notice that a failover recording server is taking over. A short break occurs, usually
only for a few seconds, when the failover recording server takes over. During this break, users cannot
access video from the affected recording server. Client users can resume viewing live video as soon as
the failover recording server has taken over. Because recent recordings are stored on the failover
recording server, they can play back recordings from after the failover recording server took over.
Clients cannot play back older recordings stored only on the affected recording server until that
recording server is functioning again and has taken over from the failover recording server. You cannot
access archived recordings. When the recording server is functioning again, a merging process takes
place during which failover recordings are merged back into the recording server's database. During
this process, you cannot play back recordings from the period during which the failover recording
server took over
Administrator manual | XProtect® VMS 2023 R1
39 | Overview
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