You need to collect packet captures (pcaps) on the SSL Visibility appliance and you are concerned about disk space. This article describes the storage location of pcaps on the SSL Visibility appliance and a method you can use to monitor disk space.
Pcap files are stored in /opt/sslv/data/pcap before they are removed from the appliance by SCP. You can check disk space before you collect the pcaps via ssh by using the command debug disk. By running this command you can view the used and available space in the /opt/sslva/data directory.