For the Linux components (Identity Server, Administration Console, SSL VPN), you should select a platform supported by SUSE Linux Enterprise Server (SLES) 10 or SLES 11. For the Access Gateway Appliance, you should select a platform supported by SLES 9 or SLES 11. For the Linux Access Gateway Service, you should select a platform supported by SLES 11.
For the Windows components (Identity Server and Administration Console), you should select a platform supported by Windows Server 2003 or Windows Server 2008. For the Windows Access Gateway Service, you should select a platform supported by Windows Server 2008.
For the hard disk, RAM, and CPU requirements, see the requirements for the individual components.