The Feeds and Speeds of Red Hat Enterprise Linux 5

Published: March 20, 2007

by Timothy Prickett Morgan

While Red Hat, like many other operating system and more complete software stack providers, wants to pitch the latest release of its software as a major change in packaging that will broaden the appeal of its products, the fact remains that for many customers, Red Hat Enterprise Linux 5 is a new and substantially improved operating system that will be sold on its own merits of features, performance, and price compared to alternatives.

There are only a few operating system alternatives of any consequence left at this point in the history of the IT business, and there are even fewer that can boast of an integrated software stack that is supported by a single vendor. IBM can say this of its Power-based AIX and i5/OS platforms and its mainframes and Microsoft can say the same for its Windows Server System, which includes Windows Server 2003 and dozens of pieces of middleware and the tools to manage the whole shebang. And while Hewlett-Packard and Sun Microsystems have well-regarded HP-UX and Solaris Unix platforms, neither has a production-grade database that they support for them--and no, PostgreSQL doesn't count, Sun, not at the level of game I am talking about--and while Sun has a middleware stack that HP does not, most of their own customers use other products. Sun has a very snazzy file system, ZFS, that has few customers so far, and HP gave up on its own clustered file system efforts and just uses Veritas products from Symantec. If IBM or Microsoft did open source software, they would do exactly what Red Hat has done with the complete stack of RHEL 5, and that is high praise.

But, again, the foundation is a very good operating system. With RHEL 5, which has been in development for two years and one month--and arguably seven months longer than Red Hat would have liked--the main story, of course, is integrated server virtualization. This was, of course, the main theme of Novell's SUSE Linux Enterprise Server 10, which was launched last July and which was the first commercial-grade Linux to come to market with the open source Xen hypervisor from XenSource integrated within it and managed from within that Linux.

RHEL 5 sports the Linux 2.6.18 kernel with a few features back-ported from the Linux 2.6.19 kernel (such as stuff for Red Hat's Global File System), and it will probably be the platform on which Red Hat sells its software stack for the next two years. Historically, according to Nick Carr, director of marketing for Enterprise Linux at Red Hat, the company has in recent years tried to keep on a schedule of putting out a new release every 12 to 18 months, but with the need to absorb the Xen hypervisor, RHEL 5 came in at 25 months. Going forward, like other operating system vendors, an 18- to 24-month update cycle is probably more likely, and two years seems most likely. None of the Unix players or Microsoft does releases any faster. Instead of doing updates, Red Hat will put out dot releases, and Carr says that the company can be expected to do about two updates a year.

RHEL 5 includes the Xen 3.05 hypervisor, and one of the things that RHEL 5.1 will have is all of the updates to Xen rolled into it, complete with a beta test cycle by Red Hat and its customers and partners. Putting Xen inside of any Linux platform is not easy, since Xen itself is changing so rapidly as it matures and as the hardware features to better support it are becoming available from Intel and Advanced Micro Devices. While Novell promised that it would be able to support SUSE Linux, Red Hat Linux, and Windows instances on Xen atop SLES 10 soon after it was announced, that support was still a little shaky even at the end of last year. Red Hat took a more conservative approach to Xen, waiting for it to mature a little more and is only promising to virtualize Red Hat instances for the moment. With Intel's VT and AMD's AMD-V hardware-assisted virtualization features, which are included in all current 64-bit chips, it is technically possible to support an unmodified instances of Windows, Red Hat did not announce such support last week.

"We're not prepared to do that right now, but we will do that a few months down the road," says Paul Cormier, executive vice president of engineering at Red Hat. As for supporting RHEL 5 instances within Microsoft's Virtual Server 2005 platforms, Cormier has no idea. "We do not control the Microsoft platform, so it is really up to Microsoft."

Like other operating system makers, Red Hat is supporting two schemes of Xen virtualization: full virtualization and para-virtualization. The para-virtualized environments do not use the VT and AMD-V features, but use tweaks in the operating system kernel to support Xen and allow software to run virtualized on plain-old regular hardware. The VT and AMD-V features do not improve virtualization support so much as they make it possible to virtualize an operating system without having to tweak an operating system to support Xen. Red Hat is supporting RHEL 4 Update 5 and RHEL 5 as guest environments on such 32-bit and 64-bit hardware platforms in para-virtualized mode. For fully virtualized environments, which use VT and AMD-V, RHEL 3, 4, and 5 are supported, and so will other third-party operating system that are certified for Xen, such as SLES 10 and Windows.

Having virtualization is one thing, but you have to have the tools to manage the virtualization, too. If anything, this is the hard point, something that the success of VMware demonstrated time and again, and indeed, what Red Hat's own stack approach to building out its business suggests. It is not Linux or Xen that matter so much, but the things you wrap around them, the integration and testing, and the tools to manage them that matter more to enterprise customers.

To that end, Red Hat has been contributing to an open source hypervisor management project called libvirt, which as the name suggests is a set of software libraries for managing virtual machines. Novell and Red Hat are both contributing to this project, by the way, and according to Carr, the goal is to have a single tool that not only spans Xen hypervisors that support Linux, but any hypervisor running on any platform. "We want it to become a standard tool for VM management," says Carr.

Red Hat has developed two tools that ride on top of libvirt, one called Virsh, which is a virtualization shell with the command line interface that system administrators will use, and the other is called Virt Manager, which is a graphical user interface for newbies. Either tool can be used to create virtual machines in RHEL 5, allocate CPU, memory, and I/O resources to them, and otherwise manage them.

As previously reported, RHEL 5 has support for iSCSI disk arrays, InfiniBand with Remote Direct Memory Access (RDMA), and the SystemTap kernel probing tool. The latter is a joint development project that includes coders from Red Hat, IBM, Intel, and Hitachi. RHEL 5 also has the Frysk system monitoring tool and support for quad-core X64 processors.

RHEL 5 comes in two flavors: the base server, which is just called RHEL 5, and the RHEL 5 Advanced Platform, which includes Red Hat's Cluster Suite for high availability clustering and its Global File System for virtualization of storage to go with the Xen hypervisor for operating systems. (See the separate story for more details on RHEL 5's packaging and pricing.)

The base RHEL 5 operating system can run on a machine with up to two processor sockets and can have an unlimited amount of main memory associated with it; this version of the software can only support four Xen-based virtual instances, however, and it does not include the Cluster Suite and GFS features that make server virtualization easier to cope with. The base product runs on 32-bit X86 and 64-bit X64 processors as well as on IBM's Power and zSeries/System z mainframe engines and on Intel's Itanium 2 and Itanium 9000 processors. The RHEL 5 Advanced Platform is not supported on mainframes, which have their own virtual storage as well as IBM's Integrated Facility for Linux or z/VM to manage virtual instances on mainframes. Mainframe shops have to use the RHEL 5 base server. The Advanced Platform is supported on X86, X64, Itanium, and Power platforms.

RHEL 5 has a lot more scalability than the prior releases of Red Hat's Linux. RHEL 3, which had some Linux 2.6 features backported to the Linux 2.4 kernel more than four years ago, was exemplary in that it could scale to 16 processors on X86 boxes and up to eight processors on Itanium, Power, or mainframe servers. (In this sense, Red Hat is talking about virtual processors, which means it is counting the aggregate number of real or virtual processor threads in the box.) With RHEL 5, X86 scalability remains at 32 processors, the same as with RHEL 4, but the Itanium platform can scale to 64 cores and 1,204 threads, the X64 platform can scale to 64 cores and 255 threads, and the mainframe can scale to six cores and 64 threads. The Power architecture remains the same at 64 cores and 128 threads. X86 machines top out at 16 GB of main memory, while Itanium and X64 machines top out at 256 GB of real memory, Power machines at 128 GB, and mainframes at 64 GB.

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