The fourth update in the Red Hat Enterprise Linux 5 family is released. From the press release: this version includes kernel-based virtual machine virtualization, alongside of Xen virtualization technology. The scalability of the Red Hat virtualization solution has been incremented to support 192 CPUs and 1GB hugepages. Other updates including GCC 4.4 and a new malloc(), clustered, high-availability filesystem to support Microsoft Windows storage needs on Red Hat Enterprise Linux. Also, support for technologies such as FCoE for storage environments and SR-IOV to improve virtual I/O performance and management included. On a side note, this article covers the upgrade procedure to RHEL v5.4 from the previous version.