Red Hat also added Aggressive Link Power Management that works (for now) only on SATA host bus adapters/controllers to jump to a low power state when there's no pending disk I/O. Coupled with aggressive use of powertop, an administrator has the ability to assert more active control over server/instance power consumption.
In an ideal future world, applications would set their use based on configuration information, but there are no real standards for this today, so administrators are left to tune application instances for power consumption.
Samba 4.0 inside
Directory service and authentication is enhanced through a new edition of Samba, open source software that provides file and print services for Windows clients. Samba 4.0 contains support for Active Directory trust relationships that work with Windows 2008 R2 Editions.
Samba 4.0 features additional support for IPv6 and connects to a System Security Services Daemon in RHEL6 that allows centralized access to different identity/authentication services, such as linking LDAP with Kerberos, Active Directory, and so on.
Products like Synchronicity and Microsoft acquisition Zoomit have provided similar directory/authentication mapping services, but RHEL6 is the first to put this into the kit.
Installation has become more sophisticated. We installed RHEL6 onto VMware ESXi, which had a configuration wrapper available to deal with RHEL6 specifics before RHEL6 was released.
The installation GUI also has detailed specs to install storage devices. If you want your server to use iSCSI or Fibre Channel over Ethernet, you get device and method-specific help and the same is provided for detected storage-area network (SAN) devices or firmware-based RAID drives.
RHEL6 also takes advantage of multi-queue networking. While we were unable to test this, we find its inclusion encouraging, as it gives administrators the capability to assign core-specific I/O tasks at a low-level, meaning that traffic doesn't have to go up and down an application stack to get CPU boosts.
Support for kernel-based KVM hypervisor virtualization is native (as it is on Ubuntu Server) and supports up to 64 virtual CPUs on virtualization-enhanced AMD and Intel server platforms.
CPU drivers (actually extensions) are available to put into virtual machines running atop KVM to enhance the virtual machine's ability to support updated CPU instruction sets.