It’s been quite some time since Red Hat refreshed its enterprise server line, and the Linux world has changed significantly since the company released Advanced Server 2.1 nearly 18 months ago.
A longer release cycle is generally seen as a benefit to enterprise server operating systems, as it eases the burden of trying to develop applications on an OS layer that’s continually changing and provides the vendor with more time to work out the kinks in the next release. This time, it’s worth the wait. Red Hat has taken its time, updated myriad supporting packages, and produced a hardened, solid OS in Red Hat AS 3.0.
There are significant core changes in AS 3.0, such as x86 support for up to 16 CPUs and 64GB of RAM (AS 2.1 was limited to eight CPUs and 16GB of RAM). The stock kernel update from 2.4.9 to 2.4.21 and the GNU Compiler Collection (GCC) update from 2.9.6 to 3.2 are welcome indeed. The less overt changes are key, however, especially Native Posix Threading Library (NPTL) integration, the inclusion of a hyperthreading scheduler, and the presence of Logical Volume Manager (LVM).
The Red Hat-designed NPTL is a significant change over the previous use of LinuxThreads, one that can mean dramatically increased performance for multithreading applications. The 2.4.21 kernel shipped with AS 3.0 is far from vanilla, incorporating several advanced features from the development 2.5 kernel tree such as the aforementioned NPTL support and integrated IPSec. Red Hat has also included AS 2.1 compatibility libraries to ease application integration during the upgrade process.
The addition of extended attributes and Access Control Lists (ACL) support at the kernel level — plus the addition of the required ACL control applications — make the implementation of Windows NT-style ACL file permissions much simpler. This in turn makes the integration of Samba 3.0 into a Microsoft network much easier, and with ACL support administrators can finally stop the manual kernel reconfiguration they were forced to do in previous distributions.
Another significant change is the AS line’s support for AMD’s Opteron 64-bit processor, building on AS 2.1’s support for Itanium and x86. (AS 3.0 also supports IBM’s zSeries, iSeries, pSeries, and S/390 architectures.) I tested the x86, AMD, and Itanium releases: The x86 and Itanium builds installed and functioned without issue, but the AMD 64 build wasn’t quite as simple.
I used new 2.2GHz AMD Opteron 248 CPUs, but the default symmetric multiprocessing (SMP) kernel wouldn’t boot — yet the uniprocessor kernel did. Compilation of several 2.4 branch kernels also exhibited this behaviour, and an installation of SuSE SuSE Linux AG Enterprise Server (SLES) experienced the same behaviour. I determined the issue was related to a bug in the mainboard BIOS of my reference system. Passing idle=poll to the kernel at boot permits the Red Hat 2.4.21ELsmp kernel to boot but forces the kernel’s idle loop to poll on the Need Reschedule flag, rather than waiting for an interrupt, which can result in performance degradation under some workloads.
On the service front, Red Hat updated Samba to the current Version 3.0 and included Apache 2.0.46 with some custom tweaks and improvements in scalability and application delivery far beyond the Apache 1.x version. Samba 3.0 includes support for full Windows 2000 integration. Prior to 3.0, Samba would integrate into an Active Directory (AD) network emulating a Windows NT server, relying on NetBIOS. With Samba 3.0, a Samba server can fully participate in an AD network, masquerading as a Windows 2000 server to Windows clients.
Run time in the spotlight
AS 3.0 superficially resembles Red Hat 9 during installation, relying on Red Hat’s simple anaconda GUI installer. During installation I noted that while the package installer offered the option of two SQL databases — PostgreSQL 7.34 and MySQL 3.23 — neither database server was actually installed, while all the accompanying client-side software was.
To take care of this, I downloaded the source Red Hat Package Manager (RPM) for MySQL 3.23 and rebuilt the RPM from the included spec file. The resulting RPM included and installed the complete MySQL client and server without a problem. Speaking of databases, Red Hat said that Advanced Server 3.0 will run every application and service Oracle offers, although I didn’t have the opportunity to test that claim. The default desktop for this release is Gnome 2.2 with Red Hat’s BlueCurve theme, and it includes a host of configuration applets using a standard layout for GUI server administration. While most Linux administrators rely on the command line to manage a server, Red Hat has continued to develop Spartan yet easily driven tools for common tasks such as package management, network configuration, BIND (Berkeley Internet Name Domain) DNS server and Apache administration, Samba SMB and NFS file sharing, printer configuration, and user administration.
Most of these tools can assist with some common administration tasks, but they are hardly soup-to-nuts complete; if you’re looking for a GUI tool to configure every aspect of Apache, keep looking. Some may find this lack of complete GUI tools problematic, but the target systems for Red Hat Advanced Server aren’t likely to be running a GUI at all, and administration is likely to be done via SSH (Secure Shell), not X11. Red Hat has also introduced the concept of layers in this release, allowing users to overlay optional packages onto the base distribution. The packages currently offered are Red Hat Cluster Suite, which provides high-availability clustering for AS systems, and Red Hat Developer Suite, which provides the extensible Eclipse IDE.
Both packages include Red Hat Network (RHN) access, as well. RHN support is much the same as it ever was, allowing administrators to manage servers via the RHN Web interface. Installing new packages is as simple as up2date — install
Officially, Red Hat does not support upgrades from AS 2.1 to AS 3.0, which will be a significant issue for those with large AS 2.1 deployments. Unofficially, you can manually trigger an upgrade option by passing Linux upgrade at the installer boot prompt. In the lab, upgrading an AS 2.1 server to 3.0 went relatively smoothly, with a few configuration-file problems and failure of binary-only kernel modules that won’t load in the new kernel. Those with third-party applications on an AS 2.1 system should either test application functionality thoroughly before upgrading production systems or perform a fresh installation. Although much of the Linux world is focused on the soon-to-be-released 2.6 kernel, Red Hat has decided to wait on deploying that kernel in this version.
Red Hat vice-president of OS development, Brian Stevens, said Red Hat would ship a 2.6 branch kernel in Version 4.0 and would be maintaining the highly customised 2.4.21 kernel shipped with Version 3.0.
He cited the significant changes in the 2.6 kernel as the main reason for keeping 2.4, and said Red Hat decided that sticking with the 2.4 kernel tree would make implementation and upgrades simpler for many customers. That said Red Hat has provided most of the packages necessary to support the 2.6 branch in this version, including adequate mkinitrd and modutils packages.
Overall, Red Hat AS 3.0 is a strong showing with only a few minor problems. The lack of a supported upgrade path will cause some short-term pain, but the long-term benefits in moving to the new version are worthwhile. Red Hat’s push to the enterprise with the AS and ES releases will be welcome for many corporations currently on the fence about Linux, but the cost structure may push small and medium businesses to other distributions that can provide similar core OS features for lower or no cost.
RedHat AS 3.0 is distributed in Australia by Ingram Micro.
RRP: Standard $2495, Premium $3995