In 1999, few Linux cluster products were available. Today, there's a different story to tell. More than half of companies that use clustering intend to increase their cluster spending over the next two to three years. Meanwhile, Linux server shipments are to outpace all other operating system platforms over the next few years. With more money being spent on clustering, Linux cluster suppliers see the opportunity, and interest in Linux cluster technology is heating up. Some Linux cluster technology is already here. More is on the way.
Clustering products can be classified as technical clusters (designed for high performance technical computing and scientific environments) or commercial clusters, which carry load-balancing clusters and high-availability clusters.
High availability is a key focal point in commercial clusters. Out of at least a dozen suppliers of Linux cluster products, many focus on high-availability cluster technology. Some suppliers also tout their product's ability to scale and increase performance, and sometimes it actually can.
As for high availability, Linux cluster offerings have lacked some of the robustness and sophistication of the more mature implementations available on proprietary Unix operating systems. However, I find the only significant features missing from some of today's Linux cluster offerings are support for cluster-wide filesystems and
single system image (SSI). That won't be the case for long. While none of today's Linux cluster products supports SSI, one or two of the Linux cluster suppliers are expected to support SSI functionality. Without the SSI capability, administering clusters beyond four nodes is not easy. At the same time, system administration for two-node clusters is not considered difficult; the lack of SSI in two-node cluster products should not be considered an impediment to adoption.
VENDORS DELIVERING
'LINUX CLUSTER PRODUCTS' |
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Competition among the Linux cluster suppliers is carried out on a relatively level playing field. Linux is basically free, there is only one Linux
kernel, Intel is the predominant hardware
platform for Linux, and no Linux cluster vendor is yet dominant.
To which degree are the products Open Source? Linux cluster suppliers are developing both Open Source and proprietary Linux cluster products. Some built their Linux cluster technology from scratch; others like PolyServe use various pieces of Open Source software such as distributed file systems to shorten the development cycle; still others have chosen to port their proprietary Unix cluster technology to Linux.
One decision facing users is whether to go with
suppliers that are small companies with significant expertise in Linux cluster technology or larger vendors with significant enterprise experience.Unix users' choices are often limited to the cluster technology provided by their proprietary RISC-based Unix supplier. Users who deploy Compaq's Tru64 UNIX realistically have only one choice, Compaq TruCluster Server. Linux users, in contrast, can select cluster technology that satisfies their specific requirements versus selections based on their operating system supplier. A user can select load-balancing cluster technology from one Linux cluster supplier and back-end it with high-availability cluster technology from another supplier. Linux cluster users also have choices between shared data and shared-nothing architectures, independent of the operating system. Besides flexible choices, Linux clusters pose another edge to Unix clusters, and that edge is cost. Unix cluster products along with their proprietary hardware typically cost several times that of relatively comparable Linux offerings. It remains to be seen if this trend continues as Linux moves more and more into the enterprise and begins to host a higher percentage of mission-critical applications. The challenge for Linux cluster suppliers will be to keep complexity and implementation costs at a level below that which is assumed by Unix cluster technology.
What else is on the radar screen? While
Linux cluster focus is strong in commercial high-availability clustering, watch Lineo
and Motorola, known for their use of Linux
in embedded systems, and Legato and
Veritas, which are known for their enterprise storage-management software.
Some Linux cluster suppliers seek to shorten their development cycle by using Open Source software components such as file systems,
distributed lock managers, and so on. Their challenge is to bring all the pieces together to produce a workable cluster technology solving the real problems that customers have.
| CLASSIFYING LINUX CLUSTER PRODUCTS |
Proprietary:
APPTIME Technologies' Watchdog; Hewlett-Packard's mc/serviceguard for
Linux; Legato's Cluster Enterprise and eCluster; Lineo's Availix Clustering;
Motorola's HA-Linux; PolyServe's Understudy and LocalCluster; SteelEye's
LifeKeeper for Linux; TurboLinux's Cluster Server 6; Veritas' Cluster Server
for Linux. |
Open Source:
Mission Critical Linux's Convolo; Red Hat's High Availability Server;
SGI's Linux FailSafe. |
| Some suppliers build Linux cluster technology from scratch;
others like PolyServe use pieces of Open Source software to shorten the
development cycle; still others port proprietary Unix cluster technology
to Linux. |
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