No archive server configured
The appliance will store session recordings on disk until the disk reaches 80% capacity at which point the oldest are deleted as space is needed to store new recordings. Recorded sessions are replicated to all cluster members.
With an archive server configured
Recorded sessions are immediately archived to the server and all members are told where to find the archived session on the server. The recordings are not replicated.
Once files are sent to the archive server, Safeguard never removes / deletes them from the archive server. You would need to set up a cron job or scheduled task to clean those up on the server itself if required.
Unique Archive servers can be assigned to each cluster member from Administrative Tools | Settings | Sessions | Session Recordings Storage Management