During the initial deployment of the Secure Web Gateway Virtual Appliance, you may configure two Virtual Disks (200GB each, by default) as cache disks for the proxy.
It is possible to add up to a total of 6 virtual disks. You can add them during initial configuration, or after deployment if the need for more cache space becomes necessary.
These virtual disks are in addition to the OS partition on which the firmware and configuration are stored.
For information on how to configure virtual disks, refer to the Secure Web Gateway Virtual Applicance Initial Configuration Guide