I've been using RHEL and its twins, CentOS and Oracle Unbreakable Linux, since day one, and I like them a lot for business server use. Of these releases, RHEL 5.4 is the most impressive of the lot, for these reasons:
1) Baked-in virtualization. This edition of RHEL incorporates KVM (Kernel-based Virtual Machine). KVM, unlike VMware or Citrix Systems' XenServer, isn't an add-on virtualization program; it's actually part of the operating system. Indeed, as the name suggests, it's built right into the Linux kernel.
As Jim Whitehurst, Red Hat's CEO, told John Fontana of NetworkWorld, "KVM makes RHEL Linux deployments look the same whether they are virtual or physical... [so] all of those thousands of man years of work put into processes and management for Linux can be applied to virtual instances."
Red Hat is not the only company to think that virtualization should no longer be an extra but instead, should be part of the operating system. Microsoft is doing the same thing with its proprietary Hyper-V technology in Server 2008 R2. Unlike Hyper-V, though, which the Burton Group for one doesn't think is ready for prime time yet, KVM is ready for both small business to enterprise data center use.
I've used KVM myself, and I'm impressed. Red Hat's KVM supports up to 16 virtual machines, each of which can have up to 256GB of RAM. And, since they work just like real machines, you can control them with the usual RHEL management tools. This is the stuff I want on my datacenter computers.
2) High-end processor support: The new RHEL also includes support for Intel Xeon Processor 5500 Nehalem EP processors and AMD Istanbul platforms. It also includes support for IBM POWER mid-range and System z mainframes. In other words, it supports the kind of hardware needed for high-end virtualization and cloud computing.
3) To really make use of all this power on the processing side, you need to be able to deploy it to clients and RHEL does this well. It now includes better support for InfiniBand and Fibre Channel over Ethernet for those times when gigabit networking isn't fast enough. RHEL also now supports smart network adapters that include processors to handle GRO (Generic Receive Offload). Network cards with GRO relieve CPUs of the burden of dealing with 10Gb and faster networks. When users, like the high-frequency traders of modern stock exchanges, want deals done in milliseconds every millisecond counts.
4) Improved programming tools. All that new speed and virtualization functionality is great, if you can use it. With RHEL's improved SystemTap performance monitoring toolset, it's gotten even easier to see what's what with your C++ applications. RHEL also now includes some new static kernel tracepoints to make life easier to monitor performance.
5) Virtual desktops ahoy? Although Red Hat didn't make a big deal about it, RHEL 5.4 also includes Solid ICE/SPICE (Simple Protocol for Independent Computing Environments) desktop virtualization and management support. Looking closely at the RHEL release notes revealed that, while there's no stand-alone RHEL 5.4 desktop coming soon, there is support for virtual desktops.
To be precise, you'll be able to boot RHEL 5.4 desktops, which run within KVM server instances, with PXE (Preboot eXecution Environment). This is still a work in progress. For example, these virtual desktops only have "Technology Preview" support at this point. In other words, don't rely on it. I'd hoped for better virtual desktop support from Red Hat, at least the basics are in there.
Want to know more? Visit Red Hat's RHEL site. I think, aside of Red Hat's reluctance to do much with the Linux desktop, you'll like it.