The following formula estimates how much space the system requires for the LAN backup for a night based on the number of users, the average number of messages and greetings measured in minutes, and the audio encoding format.
Space used each night = 100MB + 0.05MB*(L+R) + (0.1MB*M*L*F) where:
MB represents a unit of megabytes.
L is the number of local users existing on the system that night.
R is the number of remote users existing on the system that night.
M is the average number of minutes of messages per mailbox.
F equals 1 if the system uses GSM encoding, and F equals 5 if the system uses G.711 encoding.
A G.711 system with 2,000 local users with 5 minutes of messages/greetings and 50,000 remote users occupies approximately:
= 100MB + 0.05MB*(2000+50000) + (0.1MB*5*2000*5)
= 100 MB + 2600 MB + 5000 MB
= 7.7 GB.