Unix-to-Linux Migration: What Have We Learned? Your company is likely one of thousands running Linux, which became a popular option in the past two decades for edge computing (Web, firewall, file/print and mail servers) because it was more cost effective than Unix, or even Windows. Today, almost all corporations have been involved in Linux’s evolution from edge-computing solution to a suitable replacement for Unix. Until recently, x86 servers running Linux lacked the performance; reliability, availability and serviceability (RAS); and workload management of the high-end, proprietary RISC/Unix platforms used to run missioncritical database applications. Those factors are no longer barriers to the deployment of Linux to run critical business applications. Today, enterprises are migrating from Unix to Linux platforms running new, multi-core x86 servers such as the HP DL980 that overcome these limitations. Many corporations choose to begin a Unix-to-Linux migration for several reasons: pThe cost (and economics) of x86 processors is significantly lower (and better) than that of RISC/Unix platforms. pPerformance has increased to the degree that Linux surpasses Unix in many standard benchmarks. pIndependent software vendor (ISV) enthusiasm has grown to the level that thousands of business applications, including enterprise resource planning and supply chain management tools, are available on Linux. pLinux is the leader in virtualization and cloud computing — technologies that are changing the way organizations function — which Unix has virtually no chance of competing with, except in isolated situations. What We Have Learned Linux dominates in Tier 1 and Tier 2 of three-tier architectures. The biggest challenge left for the platform is to remove any doubt that it can replace Unix in hosting mission-critical database management applications that exist in the back-end third tier of the architecture. 2 X86 servers need the vertical scale of RISC servers: Initial x86 systems did not provide the vertical scale of RISC/Unix servers. They had limited CPU core counts, so the CPU and memory-intensive database tier was left to the older Unix platforms, even though these platforms were much more expensive than Linux systems. In addition, when the CPU core count in the x86 systems was low and virtualization was deployed, there were unintended consequences such as increased storage costs, complexity and inefficiency. Today, new x86 servers such as the DL980 have vertical scaling capabilities that rival RISC servers. Linux vendors are working to replicate the Unix model for integrated capabilities: Unix is viewed as a highend, integrated stack of functionality, while Linux has often been thought of as a platform in which you have to put the pieces together yourself. For example, Unix operating systems have built-in disaster recovery and tight coupling with clustering. When viewed as a replacement for Unix, Linux treated these capabilities as auxiliary components. This view of Linux is changing with the development of new Intel x86-based Xeon hardware, which includes many of the features of the RISC hardware used so successfully to run Unix. Vendors such as Red Hat are replicating the Unix model with add-ons tightly integrated with Red Hat Enterprise Linux (RHEL) 6 for capabilities that are important for resiliency and RAS. Not all vendors, however, are following the lead of Red Hat. VMware is saying that it has demonstrated that virtualization is a separate market. Likewise, Symantec is saying that it is proving that cluster software is a separate market. New Intel x86-based Xeon servers are competing with big RISC servers running Unix: It’s becoming difficult to differentiate RISC servers, such as the IBM Power 770 and Oracle Sun M9000, for most mission-critical database applications, with x86-based servers such as the HP DL980 using Intel Xeon 7500 series processors. What’s compelling about the DL980 is that there are application environments, such as databases, where scaling is absolutely critical, and the DL980 can handle the scaling requirements. What’s more beneficial is to be able to scale a database application vertically rather than horizontally. The DL980 gives you this capability. The DL980 is an eight-processor machine, with each processor available with 10 cores for a total of up to 80. Much of the scalability and increased RAS capability of the DL980 results from its utilization of the HP Superdome node controller. A good question is: Can RHEL 6 be married to the DL980 as well as AIX has been married to Power machines? The answer is yes. Red Hat is taking advantage of the features that Intel has put into its Xeon processors and that HP has put into the DL980. Red Hat knows how to leverage the machine check architecture feature set. Another feature of the DL980 is the PREMA architecture, and what it does with dynamic traffic routing and bottleneck detection. The PREMA architecture provides smart CPU caching, increasing processor scaling by reducing processor overhead and making the DL980 competitive with RISC servers. It also provides large cost efficiencies over RISC servers running Unix. We used to differentiate Unix with resource management because big Unix systems were going to run a lot of different workloads. RHEL 6 has the resource management capabilities that you can articulate in Solaris, such as containers and scheduling. And RHEL 6 supports virtualization with KVM integrated with the kernel, giving it another way to do resource management that is unavailable on most Unix systems. Intel’s Xeon and Itanium processors share a lot of the infrastructure in the way that they are linked together. The I/O hub, the QuickPath interconnect and the RAS features, along with the machine check architecture feature set from Itanium, were incorporated by Intel into the Xeon processors. The Itanium machine architecture provides a mechanism for detecting and reporting system bus, ECC, parity, cache and other hardware errors. Oracle is also a big player in Unix-to-Linux migrations, designing its database infrastructure (e.g., Oracle RAC) so that it will run on only Oracle’s Linux platform. Linux vendors are taking advantage of new x86 hardware features: Red Hat is integrating RHEL 6 with the DL980 hardware, setting the stage for RHEL 6 3 to replace Unix as the platform of choice for missioncritical database applications. In the past, you could differentiate, say, Solaris, from Linux by such factors as performance, RAS and resource management. Today, the Linux distributions are built on the 2.63 Linux kernel, which has good performance and scalability. If you do a feature-by-feature comparison of RHEL 6 with Solaris or HP-UX, you will find that there is very little missing in RHEL 6 that is available in the Unix counterparts. Linux life-cycle support expectation is vastly improved: Linux distributions from Red Hat for RHEL 6 are offered with 10 years of production phase support, followed by a three-year extended life phase. The RHEL 6 life-cycle support is designed to reduce the level of change within each major release and make release availability and content more predictable. The Oracle Linux life-cycle support also covers a time frame of 10 years. IBM’s AIX has a 10-year life-cycle support period, and HP-UX has 10 years of life-cycle support that can be extended for an additional three years. Linux releases are not published as frequently as they once were. For example, a new release announcement of RHEL occurs about every three years. Linux releases are now much better coordinated with the ISV community and with user organizations. This has helped increase the number of applications available on Linux into the thousands. New releases of ISV applications will be on Linux and not on Unix. Linux clustering can mask individual server highavailability issues: Many of the mission-critical applications running on Unix are running on Unix clusters. Clusters are used to protect against failure in a system, placing availability requirements such as five-nines for a mission-critical application on the cluster versus on individual servers. If you can meet your uptime service-level agreement with Linux clustering, then the availability question becomes harder to justify with Unix because Linux clustering is just as good as Unix clustering. Competitive Linux cluster technology is available via Veritas Cluster Server from Symantec and HP Serviceguard. Organizations are migrating to Linux to consolidate multiple Unix platforms: Server consolidation enables users to consolidate multiple Unix servers onto a single virtual host running Linux, leading to reduced costs and often increased business agility. The first step is to migrate a Unix server to a Linux server, and then perform server consolidation by moving the newly created Linux server workload to a virtual server on a Linux-based virtual host server, running KVM, Xen or VMware vSphere hypervisors. 4 Most of today’s popular virtualization technology is x86-based and essentially unavailable on Unix platforms. KVM is integrated with the Linux kernel, and Xen is open source and can be used for free. The DL980 is an excellent Linux-based virtual host server because of its vertical scaling capabilities. Summary From the beginning, Linux had its challenges — until they were met, users were reluctant to deploy the OS beyond edge computing and perhaps consider Unix-to-Linux migrations. These challenges included: pChange from an open source, publish-often life-cycle management paradigm to an enterprise operating system that meets the needs of corporate users and ISVs. pImprove RAS. pIncrease performance. pGain ISV acceptance. pSupport database applications. During the past few years, we have seen the Linux community close the gap with Unix with the advent of x86-based servers such as the HP DL980 with excellent vertical scaling capabilities and the marrying of Linux distributions with these servers. The implementation of most of the features that made RISC/ Unix the platform of choice for mission-critical, database-oriented applications, requiring high reliability, availability and scalability, are now available with selected x86/Linux servers.
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