"Can we then set up the two nodes
in datacenter 1 to send their Session Recordings to one server (mounted via
NFS) located in datacenter 1 and the two other nodes in datacenter 2 to send
their Session Recordings to another server (mounted via NFS) located in
datacenter 2?"
SWH: PAM Configuration settings (i.e., session recording) is configured on a per appliance basis. With this in mind, PAM 1 and 2 in DC 1 can be configured to write sessions in to a CIFS/NFS mount point in DC 1, while PAM 3 and 4 in DC2 can be configured to write sessions to a CIFS/NFS mount point in DC2.
"Or should the Session Recording data reside in a single place?"
SWH: If you don't write the session recordings in a single location, then you will have to log into each PAM appliance to view the session recordings for that specific appliance. Not quite operationally sound. From a user perspective, they will never remember to log into PAM 1 to look at PAM 1 recordings.
For this reason, using a single store for all recordings is advised.
Note that high latency between the PAM appliances and the session recording mount point will cause issues with recording and playback. If possible, keep the latency below 1000 ms, if you can.