November 11, 2010

Red Hat Enterprise Linux 6 Hits the Streets


It's tough to keep a secret in the Linux community. There was very little surprise yesterday when Red Hat announced Red Hat Enterprise Linux 6 (RHEL 6), but plenty of excitement nonetheless. Let's take a look at the new features and see what's in store with RHEL 6.

Since Red Hat does much of its development in the open, via its upstream work, work with the Fedora Project, and releasing public betas, the only real surprises are the actual release dates. The big new features in RHEL 6 are scalability, power management, virtualization and cloud computing, and storage.

Ready for Cloud Computing

The latest RHEL is ready to run in the cloud or be the cloud. Or both. RHEL has a bundle of resource allocation tools to help apply resource limits to system tasks, and the scalability enhancements compared to RHEL 5 are fairly impressive. The resource management tools mean that virtual guests or tasks on a host system can be constrained by CPU, memory, network, and disk I/O usage.

You'll also find a bunch of storage improvements to better handle block storage, re-size storage volumes while running, and so on. RHEL adds Ext4, so you can have larger files, better journaling, and all the goodies that Ext4 brings. If you need even more storage goodness, RHEL 6 adds XFS support as well. XFS was added in RHEL 5.4, I believe — but not as a standard option. Note that some of the RHEL 6 features are add-ons to the base OS, which means that things like scaling to 100 terabytes with XFS is going to run a bit extra on top of RHEL subscription and support.

This release comes with KVM, and without Xen. You can support up to 64 virtualized CPUs for one guest on RHEL 6 using KVM, and this release provides virt-v2v, a way to convert Xen and VMware guests to KVM. RHEL 6 does support running on Xen as a guest, but does not support running as a Xen host.

64 virtualized CPUs sounds like a lot, but RHEL 6 can support far more CPUs on bare hardware. In theory, according to Red Hat's materials, the "theoretical limit" for RHEL 6 is up to "4,096 CPUs, 33,000 IRQs. 64TB of memory, 4 million processes, and 32,000 thread per process." You don't run into too many systems with thousands of CPUs, but it does sound like RHEL 6 will be able to scale up to anything the hardware vendors want to throw at it through its lifecycle. Its lifecycle being up to 10 years for customers who want to run it that long, by the way.

RHEL 6 also benefits from kernel improvements that help the kernel stay idle more. This means reduced power usage, which is a Good Thing for data centers and organizations with a lot of computers. It's also a good thing for all Linux users, but those of us at home don't usually get five-figure power bills thanks to running hundreds or thousands of systems.

Security Improvements

Security is always a concern in the data center. RHEL 6 delivers improvements to SELinux and a new technology (to RHEL) called System Security Services Daemon (SSSD). We all know, though perhaps not love, SELinux already. RHEL 6 adds sandboxing, which allows untrusted apps to run in an isolated container. We'll cover this in detail on soon. SELinux also covers more system services in RHEL6, and adds a confined users feature. SELinux also adds the X Access Control Extension (XACE), which can help control "information flow between window objects."

SSSD is a centralized system for identity management and authentication. It handles a wide variety of directory protocols, from traditional LDAP servers to Active Directory. It caches credentials so if you're disconnected or the auth server is down, you can continue using a system.

Server Oriented

Red Hat continues to downplay the Linux desktop. The company spent very little time on talking about the improvements for the RHEL 6 desktop, but did mention GNOME and KDE were updated, and that RHEL 6 has support for automatic display detection and multiple displays, as well as the Nouveau Nvidia drivers.

Call it a hunch, but I expect more of an emphasis on client computing with RHEL 7.

Coming in RHEL 7?

Now that RHEL 6 is out the door, the natural question is "what's coming in the next release?" Yes, technology (like rust...) never sleeps.

Red Hat hasn't announced a set of features for RHEL 7, but you can get a good idea what's in store by watching Fedora closely. Note that all the big features in RHEL 6 were available in Fedora long before. SSSD was Fedora 11 and expanded in F13. The Nouveau 3D drivers were added in Fedora 13. SELinux appeared in Fedora 11. Need I go on?

The Fedora 14 release gave a few hints with SPICE desktop virtualization, and preview for the new systemd init system. I expect that SPICE will figure more prominently in either RHEL 7 or some of the point releases of RHEL 6. The last few releases of Fedora have had continuing work on Btrfs, which is likely to be stable by the time that RHEL 7 is in sight.

The feature list for Fedora 15 is fairly sparse at the moment, with just a few things like LZMA compression for the live disk, systemd, and mounting /var/run and /var/lock as tmpfs filesystems. But keep an eye on Fedora 15 as it develops, and Fedora 16. You'll see quite a few clues to what's going to be in future releases of RHEL, or at least the features being auditioned and tested.

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