So, the question is why should enterprises upgrade from earlier releases of Red Hat Enterprise Linux when RHEL 5 is officially released?
In many ways, the Red Hat Enterprise Linux 5 Beta 1 milestone release contains much of the same technology found in previous releases of Red Hat Enterprise Linux. The installation process and the resulting environment after installation of the RHEL 5 beta is quite familiar, if only just a bit more polished. If you and your organization rely on RHEL 4 as a standard email, Web, database or DNS server, RHEL 5 will simply be more of the same thing.
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All of the usual suspects are still available: the venerable sendmail program, the Apache HTTP Server and PHP, both MySQL and PostgreSQL database servers and BIND. SELinux and Red Hat Cluster Suite (possibly the two most compelling reasons enterprises should have considered upgrading from RHEL 2.1 or 3 to RHEL 4) are also included, updated to their respective current stable releases.
You might be thinking so far that none of this sounds particularly compelling to warrant an immediate rush to upgrade.
But whereas RHEL 4 shipped with Apache HTTP Server 2.0, RHEL 5 Beta 1 includes the 2.2 series Apache HTTP Server. This brings Red Hat Enterprise Linux in line with the latest Apache stable branch. With this new stable branch comes several significant changes, including a new structure for authorization and authentication security modules. The caching modules mod_cache, mod_disk_cache, and mod_mem_cache have been improved, and new modules have been added to provide proxy load balancing and modular SQL database support.
In addition, Apache 2.2 will support file sizes larger than 2GB on 32-bit hardware platforms. These are all features an enterprise can take advantage of to increase performance and scalability, but some of these changes and enhancements will necessitate Apache HTTP Server configuration updates and possibly custom application upgrades for compatibility. Apache provides a resource for upgrading from Apache HTTP Server 2.0 to 2.2 at http://httpd.apache.org/docs/2.2/upgrading.html.
Also affecting some enterprises' LAMP solutions is the inclusion of PHP 5.1 in Red Hat Enterprise Linux 5 Beta 1. RHEL 4 shipped with PHP 4.3.
Perhaps you have already upgraded PHP to 5, building your own custom installation from source or binary distribution. Upgrading to RHEL 5 would allow you to rely on Red Hat's packaging, taking advantage of the latest PHP features and performance improvements without having to worry about rebuilding your custom installation every time a new security or bug fix is released. But with the release of PHP 5.1, significant changes to the language means that older PHP 4 code may have to be modified. A resource detailing more about the migration of PHP 4 scripts to PHP 5 is available at http://www.php.net/manual/en/migration5.php.
RHEL 5 Beta 1 is based on the latest stable Linux kernel version 2.6.18. RHEL 4 is based on Linux kernel version 2.6.9. Several enhancements and improvements have been developed in the Linux kernel, too numerous to list here in detail. Of particular note are significant scalability improvements, support for file sizes up to 16TB within the Ext3 file system and the inclusion of FUSE, a new API designed to support file systems in user space.
Although some upstream kernel improvements have been back-ported and included in RHEL 4 for some time, the vast majority of new scalability and performance features will not be added to RHEL 4.
If you are pushing the envelope in terms of scalability or find you need additional system performance, the Linux kernel improvements found in the beta release of RHEL 5 should heighten your interest in upgrading. An excellent resource for information regarding upstream Linux kernel development and improvements in the latest stable Linux kernel can be found at http://kernelnewbies.org/LinuxChanges.
With the release of Red Hat Enterprise Linux 5 Beta 1, Red Hat has introduced Stateless Linux to its enterprise customers. Originally developed in the Red Hat Enterprise Linux proving grounds, Fedora Core, Stateless Linux is a new architecture for easing the provisioning and management of many systems. Supported features in RHEL 5 Beta 1 are limited, so using Stateless Linux in an enterprise production environment is not recommended. Considered a technology preview of things to come, this is certainly a feature to check out and keep an eye on.
More information about Stateless Linux is hosted by the Fedora Project at http://fedoraproject.org/wiki/StatelessLinux.
I've left one feature that has generated a lot of buzz for last: Xen, the open source virtualization software. Red Hat Enterprise Linux 5 Beta 1 includes packaged support for Xen on i386 and x86_64 hardware platforms. Xen allows for the ability to run one or more virtual servers within a single host OS on one physical server.
Of course, the uses of such a technology are numerous. For example, if you are in the business of providing virtual Web hosting to customers, you will find value in the inclusion of open source virtualization technology -- technology previously not easily implemented with earlier releases of Red Hat Enterprise Linux. The inclusion of Xen seems to indicate Red Hat feels the technology is ready for prime time, perhaps additional reason to upgrade or purchase an additional Red Hat Enterprise Linux license.
So, the Red Hat Enterprise Linux 5 Beta 1 public release certainly offers an impressive selection of updated, improved, and new technologies.
For those of us satisfied with RHEL 4 in a standard LAMP environment, I do not think there will be reason enough to rush to upgrade just for the sake of upgrading. RHEL 4 contained significant improvements that have proved to be a solid platform for the enterprise. This is certainly the case for those that don't use the Red Hat packages of key software, like the Apache HTTP server, PHP, and MySQL.
But if you find your environment demanding increased performance, pushing the envelope in scalability, or if you find value in enterprise support for open source virtualization technology, you should consider an upgrade. Take the public release of Red Hat Enterprise Linux 5 Beta 1 for a test drive, and keep an eye on subsequent previews of what's sure to be Red Hat's finest enterprise offering yet.
Curtis Smith is a professional systems and network administrator residing in Westerville, Ohio. His experience includes designing, building and maintaining open source email and Web solutions for an Internet service provider and the Max M. Fisher College of Business at The Ohio State University. Curtis is the author of Apress' Pro Open Source Mail: Building an Enterprise Mail Solution.