"Several improvements affect virtualisation. The x64 version of
Xen now supports up to 126 processors and a Terabyte of memory. The
paravirtualised network and mass storage drivers for fully
virtualised RHEL-5 guest systems have moved into the kernel, and a
separate installation is no longer required. Virtio drivers improve
the performance of guest systems under the KVM alternative.
Features like extended page tables that are included in recent x64
processors are now supported, which is likely to increase the
performance of fully virtualised guests.
"Red Hat has also improved cluster operation. The distributed
Global Filesystem (GFS) 2 is now officially supported, and fencing
has been improved in several minor ways. RHEL 5.3 supports the
encryption of root and swap partitions. The developers updated a
number of system tools, for example the cups print server, the rpm
and yum package management tools and the SystemTap tracing tool.
Red Hat Enterprise Linux now offers the free OpenJDK Java
development environment which, according to Red Hat, fully complies
with the Java SE 1.6 Compatibility Kit."