Next O.S. can be resized (CPU and RAM) without reboot. Resize can be UP or DOWN.
CentOS 5.9 x86
CentOS 5.9 x64
CentOS 6.3 Plesk11 x64
CentOS 6.3 cPanel x64
CentOS 6.4 LAMP x64
CentOS 6.5 x64
CentOS 6.5 x86
CentOS 6.5 DirectAdmin x64
Red Hat Enterprise Linux 5.9 x64
Red Hat Enterprise Linux 6.4 x64
CDP r1soft x64 xen
Scientific Linux 6.2 x64
Scientific Linux 6.2 x86