As the name suggests, this is the second major update to Red Hat’s Enterprise Linux 3 since it was launched in October 2003. This iteration includes support for the new 64-bit Xeon processors, which should start shipping imminently.
When Enterprise Linux 3 was announced in October, Red Hat said that it was not going to jump on the Linux 2.6 kernel bandwagon, particularly since it had back-ported many of the advanced features of the Linux 2.5 development version (the precursor to the latest Linux 2.6 kernel) to the Linux 2.4 kernel that was at the heart of Red Hat’s Linux Advanced Server 2.1 and the new Enterprise Linux 3. So if you expected a kernel change with Update 2, forget it. If you want to play around with Red Hat’s interpretation of Linux 2.6, you will have to use the Project Fedora or wait until next year when Red Hat rolls out a true Linux 2.6 kernel, and probably one with goodies brought back from the future Linux 2.7 development release, if history is any guide.
When Enterprise Linux 3 came out, it was the first implementation of Red Hat’s Linux that used the exact same kernel–in this case, Linux 2.4.21–across workstations, servers, and clusters built from 32-bit and 64-bit Intel, 32-bit and 64-bit Advanced Micro Devices, and 64-bit IBM Power (iSeries and pSeries) and zSeries platforms. Prior to this, different platforms had different kernels and different code-bases, which radically complicated the idea of making a consistent set of applications available across those platforms. So Red Hat is not about to make any bold moves that would upset this balance it has just achieved.
With Update 1 of Enterprise Linux 3, which shipped in mid-January of this year, the main improvements were to speed up the performance of non-uniform memory architecture (NUMA) clustering, which is the basis of many high-end server architectures these days even though server makers claim that they are selling servers that use symmetric multiprocessing (SMP), an alternative means to gang up processors. Update 1 also had improvements to the memory subsystems that allowed larger databases to be created on Red Hat machines and fixes for clustering software, which Red Hat sells as a separate item with this version (but which used to be bundled in with Linux AS 2.1). Update 1 also had tweaks to improve the performance of Linux on Power, Opteron, and Itanium processors and had drivers to support a wider variety of these machines.
Update 2, which will be available to Red Hat customers with support contracts through the Red Hat Network, is interesting in that it will support the Nocona chip from Intel, the first Xeon processor to support 64-bit memory extensions. The release notes say that there is a new ia32earchitecture in the code base that can support either the Intel Xeon or AMD Opteron versions of the 64-bit extensions to the 32-bit X86 architecture. The existing x86_64 option, which was optimized specifically for the Opterons, will continue to be available. Red Hat says that the kernels for both of these options, ia32e and x86_64, are built from the same x86_64 source code; so it looks like Intel reverse-engineered the memory addressing subset of the Opteron to make the 64-bit Xeons. (This is something that VMware has confirmed Intel has done, and the reason VMware knows this is that the code it created to support its Workstation, GSX Server, and ESX Server partitioning on Opterons ran unchanged on the Xeon-64s.)
The update also includes support for IBM’s PowerPC 970-based JS20 BladeCenter blade servers, various tweaks for the PowerPC and Power architecture (but no support for the just-announced Power5 processors, which are not expected to be supported until the third quarter of this year). The update also has an on-demand timer facility that reduces idle CPU overhead when Linux 3 is installed on IBM zSeries mainframes. A slew of new disk drivers, network drivers, and improvements in the VM, NFS, IPv6, and SCSI subsystems round out the improvements in Update 2, and the usual gang of changes to improve security and to stop race conditions and resource hogging are in the 140 patches that comprise the update.
Customers are warned to make sure that all previously released errata relevant to their particular edition of Enterprise Linux 3 have been applied to their systems before applying Update 2, which is not a cumulative patch.
