This is covered extensively in Secure Knowledge, the following reference SKs should help further to the above...
sk92907: Threat Emulation inspection failure due to disk space shortage
sk101149: "Error: Disk space usage is above allowed value" is displayed in SmartView Monitor for Threat Emulation blade
Related solutions:
sk33997: How to find directories and files that are using a large amount of disk space
sk63361: How to clean up disk space on a Security Gateway or Security Management Server
sk60080: Disk space tips and tricks for SecurePlatform / Gaia / IPSO / Linux OS
sk91060: Removing old Check Point packages and files after an upgrade on Security Gateway / Security Management Server
CCSM R77/R80/ELITE