When we pitted Red Hat Enterprise Linux against several flavours of UnitedLinux to see how each fared as an enterprise server platform, we found each edition of the popular GNU/Linux operating system to represent a distinct method on how to build bare metal into a working server. Installation is different, configuration options are different, and hardware support varies across these Linux flavours.

We selected Red Hat's Enterprise Linux as the Blue Ribbon winner in this test because while the systems were somewhat comparable in terms of performance and management wares, Red Hat offers more hardware support, is easier to configure and offers more security options.

Red Hat Enterprise Linux comes in numerous flavors, ranging from a US$179 desktop/workstation edition called Enterprise Linux WS Basic Edition to the Enterprise Linux AS Premium Edition we tested. The premium edition, which costs about $2,500, is distinguished from its siblings by clustering capabilities, additional hardware support and service options.

UnitedLinux is a consortium of product/service vendors, comprising founding Linux operating system distributors SuSE Linux AG, The SCO Group Inc., Conectiva SA and TurboLinux Inc., and application vendors such as Oracle Corp., which contributed Oracle 9i to the mix. This consortium is an effort to bring a standard code, feature and configuration set to Linux distributions so that applications developed under UnitedLinux can take advantage of standards in each UnitedLinux product.

The code base and infrastructure of UnitedLinux editions has SuSE Enterprise Linux as an ancestor. A modified SuSE YAST2 front-end installation program serves as a common denominator among the four UnitedLinux versions and ensures that setup among the distributions is identical. But after installation, each UnitedLinux edition branches out to suit a target market.

Initially, all four consortium members offered distributions for this review. But SCO pulled its support for UnitedLinux, and pulled out of this review.

We reviewed the SuSE UnitedLinux version extensively, but because the Conectiva and TurboLinux versions are focused on the Brazilian/Portuguese speaking and Southeast Asian markets, respectively, we did not test them extensively.

While neither SuSE UnitedLinux nor Red Hat's distribution strayed from its Linux Standards Base (a reference platform that ensures that all applications can run across Linux distributions), hardware support favored Red Hat, if only for a larger driver base and advanced hardware detection. But we found that all hardware items were discovered and configured correctly, with few mistakes made by each distribution vendor. All UnitedLinux distributions behaved identically.

The custom-installation option on Red Hat offers a variety of choices relating to what software you want installed, disk partitioning, and boot loader selection. Alternatively, an installation wizard can make these choices for you. The wizard worked well and mostly made astute choices, although it divided our disk arrays into seemingly bite-sized devices with seven partitions. By contrast, the UnitedLinux distributions divided the two disks we used into larger chunks, which is a better way to reserve server space for future operations.

Red Hat also let us enter a network address, but didn't probe the network for other settings, such as a DNS server or gateway, and incorrectly guessed what those were. It also identified sound devices that didn't exist in our hardware. Red Hat easily understood the number of platforms we installed it on, including the symmetric multiprocessing boxes.

Red Hat's wizard then let us select high, medium or low security settings, gradients that were customizable after installation but also have a strong bearing on initial functionality. The security setting choice is important because the installation program leaves the server in remarkably different conditions from a communications standpoint. Servers are used for many purposes: For example, the gradient of security needed to tailor a server for a Web server as opposed to an application server can be very different. Red Hat's security choices let us easily position the server for gradients of service that otherwise take a long time to manually adjust settings in individual applications.

The default installation can place as little as 61M bytes or as much as 1.5-plus G-bytes if you install all software packages (full firewall, e-mail, Web services, development components and the like). The drivers that the operating system chose initially weren't necessarily the most recent or stable versions, but Red Hat, like UnitedLinux/SuSE, doesn't do an Internet search to find up-to-date drivers such as Windows server platforms.

As previously mentioned, the UnitedL/SuSE version uses a rendition of the YAST2 installation program. This UnitedLinux variation of YAST2 differs from the tool found in other SuSE versions in that the default number of software packages installed is much smaller. The only difference among the three UnitedLinux installation applications was the ability for each application to subsequently install version-specific applications that would run on each server, such as mail, firewalls and development environment.

Each UnitedLinux distribution has three common CDs, with up to three more offered that include distribution-specific add-ons. These add-ons can be important; we found a dearth of useful tools in the base UnitedLinux and welcomed the SuSE CD that included wares to configure network resources and automate system setup.

UnitedLinux correctly found all the hardware devices in our platforms but couldn't readily detect the four-Xeon CPU configuration in our HP ProLiant DL580 server; Red Hat found it without assistance. After we changed a BIOS value, UnitedLinux correctly found the multi-CPU configuration and adjusted to it.

Up and running

We performed our tests on an HP ProLiant DL580 server with ext3 filing system, a journaled file system that has proven to be more resilient than the 'native' ext2, the traditional Linux default setting, and a RAID 1 (mirrored single drive) configuration. Both UnitedLinux and Red Hat recovered from a simulated drive failure. A simulated CPU failure test proved more difficult, as Red Hat survived but UnitedLinux/SuSE froze. After our testing, SuSE provided settings that it said should prevent this problem.

Network load balancing on the HP ProLiant DL580 also was difficult for SuSE, which took about 10 seconds longer than Red Hat to recover from an ipchained (ipchain is a TCP/IP protocol management method) network card connection termination test.

Both distributions can emulate NetWare 2.X servers and AppleTalk Servers. Built into both is support for Samba, which can emulate Windows NT primary domain controllers. We found that the UnitedLinux/

SuSE-specific controls gave us more automated control over Samba.

Both UnitedLinux and Red Hat support a variety of VPN methods, including IP Security, Secure Sockets Layer, SOCKS5 and even Microsoft's Point-to-Point Tunneling Protocol VPN method. Red Hat supports several different encryption methodologies, ranging from RSA RC3 to Enfish.

Both products support network card traffic load balancing. In our tests, we found little difference between the distributions because they use similar applications for load balancing.

We made several tech support queries to SuSE and Red Hat using a third party's credentials. We sent via e-mail four questions to both providers that ranged from neophyte to advanced, to both providers. Red Hat replied with the answers within an average of two hours, and SuSE within eight. All answers were correct, but the replies from the Red Hat staff added more information about the suggestions they proposed.

Performance

To assess performance, we looked at two types of measurements that we've also used in our Windows 2003 assessment.

The first suite of tests checks Web performance characteristics.

Both versions of Linux tested run Apache as their Web engines, which we installed on an HP ProLiant DL580 platform (see How we did it). Both versions performed comparably to each other and quite well against Win 2003 that we tested on the exact hardware platform two months ago.

Red Hat topped its competitors in our transaction-per-second test, in which we tested static Web page transaction cycles - downloading 20 4K-byte files per connection as a transaction cycle and our maximum open TCP connections test. The latter test gauges how many open TCP connections (relationships) the Web server and underlying network connectivity can sustain. Red Hat beat Win 2003 and United Linux/SuSE in the latter by as much 10 percent and 20 percent, respectively.

UnitedLinux SuSE edged out Red Hat and Win 2003 to gain the best numbers in our test of maximum TCP connections/sec test, which measures the capacity of the server to respond to TCP session requests.

With a goal of assessing each product as it ships, we used default settings for both versions of Linux and Win 2003, and we do not implement experimental settings changes that vendors often suggest.

In our second set of disk tests, performance numbers between Red Hat and UnitedLinux were within a 5 percent margin. With the journaled ext3 filing system kicked in for both Linux operating systems on the HP ProLiant DL580 platform, both copied large files 8 percent faster (after a 5 percent margin of error) than Win 2003. For example, an interfolder file copy using cp, the Linux copy function, of an 800M byte file took 32 seconds to copy under UnitedLinux/SuSE, whereas using a CMD copy command under Win 2003 took 40 seconds to execute.

Red Hat consistently recovered from simulated outages more quickly than UnitedLinux/SuSE but within the margin of error.

We installed the K Development Environment user interface on Red Hat and were impressed by the number of tools Red Hat supported, including a service configuration that let us enable service daemon launch and sculpt command-line arguments associated with them. A Kickstart Configuration tool sets up basics quickly, such as server authentication methods (such as Lightweight Directory Access Protocol, Samba and so on), network, firewall, boot options, installed software packages and the like. YAST2 doesn't provide as many configuration options in a GUI until UnitedLinux-specific extensions are added. When they are, UnitedLinux/SuSE comes much closer to Red Hat's options, but still lacks both management options and structure for them.

Deciding factor

As the comparable performance numbers show, these products are both basic Linux at the core. But in the end, we were decidedly more satisfied overall with Red Hat's hardware integration strengths and security configuration options.

Henderson is principal researcher for ExtremeLabs, of Indianapolis. He can be reached at thenderson@extremelabs.com.