Chapter 15 Unified Threat Management for FortiOS 5.0 : Other Security Profiles considerations : Monitoring Security Profiles activity : Configuring packet logging options : Limiting disk use
  
Limiting disk use
When logging to the FortiGate unit internal hard disk, you can define the maximum amount of space used to store logged packets.
config ips settings
set ips-packet-quota 256
end
The acceptable range is from 0 to 4294967295 megabytes. This command affects only logging to disk.