WHITE PAPER Migrating from Unix to Linux to Achieve Operational Benefit - Dell
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WHITE P APER
www.idc.com
Migrating from Unix to Linux to Achieve
Operational Benefit
F.508.935.4015
Sponsored by: Dell Computer
Al Gillen Mark Melenovsky
July 2003
P.508.872.8200
SITUATION OVERVIEW
The economic downturn of 2001 and 2002 changed how customers and IT managers
think about selecting and configuring their server solutions. Integral to this shift is
increased interest in low capital-cost alternatives such as Linux servers – which are
gaining considerable market share as shipment rates grew at double-digit rates year-
Global Headquarters: 5 Speen Street Framingham, MA 01701 USA
over-year throughout 2002 and into Q103. The strong growth in this market segment
is in turn accelerating the industry's acceptance of new suppliers and new
technologies.
Although significant attention has been paid to Linux solutions, IT organizations
continue to invest heavily in Unix/RISC servers. The Unix/RISC installed base
represents many billions of investment that were made over a period of many years.
During the late 1990s, annual spending for Unix/RISC servers averaged more than
$20 billion per year. In 2002, Unix/RISC accounted for 38.6% of the worldwide server
revenue, yet only 11.0% of the shipments. This reflects the higher average sales
prices for scalable Unix servers in the midrange and high-end price bands.
IT organizations today are being pressed to freeze or reduce their annual budgets for
new hardware acquisitions, ongoing maintenance and operations, and personnel
costs. In the case of Unix/RISC servers, customers often are seeking more
economical alternatives for the necessary capabilities and performance. Increasingly,
customers are finding the solution in the form x86 servers and “scale out” clusters
running Linux.
The programming and operational similarities of Linux and Unix are well-known.
Although the operating system kernels were built independently, the surrounding
utilities and shells often are similar or identical. This leads to application-development
and deployment environments that are similar enough to allow existing IT staff to
transfer workloads from one platform to another — providing that the application code
and software skill sets are available. Thus, the differences between these two
computing environments do not preclude Linux servers from being deployed to
support workloads that once were the sole province of Unix servers.
Differences do exist, including fewer off-the-shelf packaged applications for Linux;
less scalability on any individual server node in Linux servers; and higher use of Linux
for "edge", Web, and HPC workloads than for traditional business workloads.
However, IDC believes that these aspects of the Linux server ecosystem will change
quickly in coming years, making Linux servers more entrenched in the overall IT
environment.FIGURE 1
WORLDWIDE SERVER SHIPMENT SHARE BY OPERATING SYSTEM (2001-2007)
100%
90%
80%
70% Other
60% Novell
50% UNIX
40% Windows
30% Linux
20%
10%
0%
2001 2002 2003 2004 2005 2006 2007
Source: IDC, 2003
FIGURE 2
WORLDWIDE SERVER SPENDING REVENUE SHARE BY OPERATING SYSTEM (2001-2007)
100%
90%
80%
70% Other
60% Novell
50% Unix
40% Windows
30% Linux
20%
10%
0%
2001 2002 2003 2004 2005 2006 2007
Source: IDC, 2003
2 #3814 ©2003 IDCAs can be seen in Figure 1, IDC expects Linux server shipments to continue to grow through the year 2007, which is the end of the current forecast period. This expected growth carries forward a period of double-rapid-growth that took place throughout 2002, even as many other segments of the worldwide server market continued to decline. Figure 2, above, illustrates spending for Linux-based servers to grow substantially, over time, growing from $2 billion in 2002 to more than $7 billion by 2007. WHY MAKE THE MOVE TO LINUX? O P E R A T I O N A L B E N E F I T S A N D I S S U E S O F U N I X / L I N U X M I G R A T I O N Over the past few years, Linux has emerged as a credible alternative solution to traditional Unix system deployments, particularly for basic infrastructure workloads traditionally found behind the scenes at businesses, governmental organizations, and universities. Linux was intended from its introduction in the early 1990s to deliver a Unix-like experience, and because Linux draws on many of the same utilities and applications used in Unix, the parallels between these two environments, for programmers and for system administrators, are remarkably strong. Early deployments often took the form of a basic network service, such as a print server, file server, Web server, or firewall system These early workloads generally were not dependent upon layered infrastructure software such as transaction processing software, database software or application server software, and were typically invisible to end users and executive management. If an organization's needs were to outgrow the capabilities of the Linux system, or should the Linux prove unsuitable to the workload assigned, a Unix system could easily be substituted with little fanfare. After proving itself in these less glamorous roles, Linux now is increasingly being seen as a solution suitable for more demanding business workloads. The introduction of commercial software ranging from databases, Web application servers, middleware, infrastructure software and management tools, it is apparent that Linux now offers a software stack that can be a credible alternative to Unix systems. In particular, the move of Oracle and other vendors to port its database products to Linux is exactly the kind of industry support that lends credibility to the power of the open-source software movement. By offering equal or higher capabilities along with better price/performance than competitive technologies, users can explore the possibility of migrating elements of their installed base Unix/RISC servers, over time, to more cost-effective volume server systems (servers priced less than $25,000) and to midrange enterprise server systems (servers priced from $25,000 to $499,999). ECONOMICS Past IDC studies on total cost of ownership (TCO) consistently found that the most significant cost item associated with a 3- or 5-year TCO calculation is the IT staffing cost. Considering the similarity between Linux and Unix software environments, it is not surprising that hourly staffing costs for full-time equivalent (FTE) administrative personnel are similar. However, these IDC studies have also found that for some workloads, Linux servers can have a lower TCO, especially for Web-enabled workloads and infrastructure workloads. These differences often are the result of less complicated – and therefore less costly – configurations on the part of the Linux systems. ©2003 IDC #3814 3
But in addition, earlier studies have found that hardware and software acquisition costs tend to be lower, as well. The lower hardware acquisition costs are due to the overall system design — since multiple, smaller servers will be connected together into clusters running parallel databases, such as Oracle 9i RAC, which maintain a virtual computing resource across the entire cluster. In many cases, this configuration can lead to cost savings on initial purchase price, and may also offer attractive maintenance costs compared to Unix/RISC systems. The lower software costs were initially due to the early deployments that tended to include considerable use of open-source software that was acquired at little or no cost. Today, Linux system-software costs may in some cases, be equivalent (where ISV software licenses are based on a per-processor basis), and in some cases less, than software stacks for other server operating environments. Importantly, both staffing costs and downtime costs figure in prominently in typical Linux TCO calculations, while staffing costs and hardware/software acquisition costs tend to dominate TCO calculations for Unix system configurations. While it continues to be possible to build low-cost configurations of Linux and application software, the server market is gradually shifting, over time, to favor increased use of licensed software for fees. Software configurations deployed on Linux platforms fall into two general categories: commercial software products from ISVs, or commercially supported open-source products that carry a use fee in exchange for the commercial packaging and support services. IDC software research has found a high degree of correlation between the presence of Unix skills (programming and system administration) and readiness to move to Linux for both high performance computing (HPC) and commercial applications. On the vendor side of the equation, systems management vendors such as BMC, Computer Associates (CA), HP (OpenView), IBM (Tivoli) all have moved quickly to support Linux as if it were another version of Unix. OTHER KEY BENEFITS The architectural flexibility of the IA32/x86 architecture systems, based on Intel or AMD microprocessors, offers a tangible benefit to IT customers, particularly in configurations for which multiple operating systems, including Linux and Microsoft Windows, are available. In 2002, IDC data shows double-digit growth for x86 servers running Linux and for x86 servers running Windows. Growth rates for Linux servers were faster than for Windows servers, although based on a smaller number of server shipments. The trend toward dynamically configurable and dynamically provisioned configurations is favorable to the use of an industry-standard hardware architecture, providing commodity low-cost server systems made by many vendors, that gives users the ability to integrate new systems into future utility computing configurations comprising multiple servers, multiple operating systems and multiple workloads. L I N U X I S A L R E A D Y A S T A P L E O F H P C C O M P U T I N G Linux is in use at many high-performance and technical computing facilities around the world, particularly at government institutions and laboratories. Reliability, low cost of acquisition, ease of customization, and its Unix-like heritage are all significant factors in promoting its adoption. Users at such facilities tend to be ahead of the curve when it comes to knowledge and practice of IT, further fueling growth. Linux clusters typically are deployed with many small Linux servers (most of them uniprocessors or dual-processors), fast interconnects between the servers, workload- balancing or clustering software and attached storage resources. HPC workloads are easily deployed on such Linux server clusters, as their computing tasks can be divided up and assigned to individual servers within the cluster. Linux use in the HPC field is already widespread, due to the presence of Linux programming and system- 4 #3814 ©2003 IDC
administrative skill-sets, and due to the early adoption of new technologies by HPC sites, which typically favor custom deployments and hands-on support for systems. THE MOVE TO COMMERCIAL COMPUTING ON LINUX SERVERS The porting of commercial infrastructure software to Linux from Unix, has been ramping up in recent years. Today, a significant portion of the infrastructure software required by commercial application software aboard Unix is now available for the major Linux distributions. This enables Linux to offer a functionally competitive deployment environment to a Unix/RISC system. A second element, systems management products, are now available for Linux servers and Linux distributors have been working to build Linux-specific solutions to handle patch management, upgrading, and system configuration. Solutions have emerged from Linux software distributors, such as Red Hat's Red Hat Network, SuSE's YaST, and Ximian Corp.'s Red Carpet Enterprise. These solutions deliver variations of system configuration and provisioning that leverage a centralized update server that may be located inside or outside a company's firewall. While managing a Linux system may seem to be a daunting task for an organization with no experience in Unix, the typical Unix shop can add additional Linux servers and support those with little fanfare, often by using existing tools and processes. With these required elements in place, Linux systems are now poised to absorb commercial workloads previously supported by Unix servers. Another key element, database support is even more mature aboard Linux operating systems. Commercial computing can also be done in clustered configurations, using parallel database products such as Oracle 9iRAC and IBM DB2. The commercial packaged applications (i.e., ERP, financial analysis) available to run on top of these parallel databases are important, but relatively small in number, compared with those for HPC applications, but the number of ISV commercial applications being ported from Unix to Linux is expected to grow rapidly over the next few years. DATABASE ENGINES FOR IT WORKLOADS Support for database engines and database applications has been one of the leading drivers for Unix server adoption for many years, IDC Workloads research has shown. The stability of the Unix operating system itself, along with the proven capability of scalable Unix servers to support growing databases has made Unix servers a mainstay of the scale-up database computing environment. In its early phases, Linux server adoption was not directed toward database use, with the exception of small database engines for Web-related workloads, and of personal databases or of databases deployed to support small numbers of end-users. Today, Linux servers are being deployed in new ways, particularly with respect to support of parallel databases, such as Oracle 9iRAC and IBM DB2. These database engines are deployed, in pieces, across multiple small Linux servers. Then, through the use of virtualization technology, the individual "slices" of the database can be viewed a s a single, larger database image. More end-users can be supported in this way, and individual end-users are unaware of the fact that the database image is running across two or more Linux server machines. D E L L ' S S T R E N G T H S I N T H E L I N U X S E R V E R M A R K E T As the market leader in the U.S. x86 industry-standard server market, Dell has a portfolio of proven, Intel-based servers addressing customer demand across a range of server workloads and applications as well as customer environments. Figure 3 ©2003 IDC #3814 5
below illustrates Dell's growth in the U.S. server market over the course of the last
five years. As Linux has proven itself to be a viable enterprise server operating
environment over the past five years, Dell has been one of the leading companies in
the industry to actively promote Linux servers and to build a suite of HPC and
commercial server solutions built around Linux servers.
FIGURE 3
U.S. SERVER SHIPMENT MARKET SHARE FOR DELL AND LINUX-BASED SERVERS, 1998-2002
30%
25%
20%
15%
10%
5%
0%
1998 1999 2000 2001 2002
Dell Linux
Source: IDC, 2003
The economic downturn of 2001 and 2002 continues to influence how customers and
IT managers think about their server solutions, and about low capital-cost
alternatives, such as Linux servers that are gaining considerable market share as
shipment rates grew at double-digit rates, year-over-year throughout 2002 and Q103.
This economic environment is accelerating the market's acceptance of new suppliers
and new technologies. Four years ago, Dell's server business was heavily weighted
to the small and medium business (SMB) customer segment and to the small office.
Today, rack's of Dell servers can be found in many corporate data centers tackling
mission-critical workloads. Much the same can be said of Linux. Four years ago,
Linux was found primarily in front-end server applications in the technical computing
market or as servers for hosting web sites. Today, Linux is beginning to be adopted in
the packaged applications market and as a platform for databases, such as Oracle.
Corporations today are under pressure to reduce costs while increasing their IT
infrastructures capabilities. Additionally, the need for a more flexible technology
foundation is becoming increasingly apparent among many customers who see their
businesses changing over time, but their server and storage solutions remaining
static. These customers have undergone costly "rip and replace" exercises to adapt
their technology to their evolving business models, and would prefer to avoid doing so
again in the future. Industry-standard server solutions provide a more flexible
6 #3814 ©2003 IDC"building block" approach to a customer's IT challenges. By having a more standard infrastructure, server solutions can be optimized and redeployed much more cost effectively than a more proprietary systems. D E L L ' S B U I L D I N G - B L O C K A P P R O A C H T O D E P L O Y I N G L I N U X S E R V E R S Dell has taken a comprehensive, building-block approach to assisting customers who are making a move from Unix servers to Linux servers. The building blocks include the following: server products and associated storage products; ROI tools that allow IT organizations and senior management to discover the return-on-investment for their planned Linux server systems; services (including consulting services, deployment and support); and provision of case studies and best practices, which will allow prospective customers to learn about successful Linux server adoption by other It organizations. Details about these four building blocks follow: POWEREDGE SERVERS AND EMC STORAGE Dell is the U.S. market share leader for Intel-based servers. Dell PowerEdge servers can be clustered together to run HPC applications or commercial workloads. Dell has partnered with EMC, of Hopkinton, Mass., to provide storage systems for a range of commercial and technical solutions including Linux server clusters. Both companies have established a very close enterprise relationship and work together to provide server/storage support for these clustered Linux server solutions as well as a full range of commercial applications and databases. The partnership has enabled both companies to create value for their enterprise customers and prospects and has helped build Dell into one of the leading providers of storage solutions in the industry. SUPPORT FOR LINUX DISTRIBUTIONS Dell has long held a close relationship with Linux vendor Red Hat, Inc., via the One Source Alliance agreement for joint engineering and marketing activities. Dell is also working with the Linux distributor SuSE in terms of a certified operating system and a cooperative technical support agreement. In addition, the company has partnered with Oracle and Red Hat in developing the Oracle 9i RAC solution set that is sold with Dell's PowerEdge servers. In response to its growing Linux business, Dell has expanded its professional services and support organizations to help customers move from Unix systems to Linux systems. Dell's ability to work closely with Linux distributors, particularly the market leader Red Hat, in providing timely and effective support, including escalation for resolution of system-software problems, will be an important element of ensuring customer satisfaction with Dell's Linux cluster configurations. DELL'S SUPPORT OF ORACLE 9IRAC DATABASES The central fact of Oracle database technology is that the features and functions are "baked into" the software, and that the Oracle database product can be brought forward from AlphaServer or Unix/RISC server platforms, or ported, into new platforms — like Linux x86 servers — a process that confers the same Oracle feature/'function set on the new platform that was available on the older platforms. In addition, Oracle is leveraging the Oracle Clustering File System (OCFS) as a global file repository that can be accessed by all the Linux servers in a Linux/Oracle 9iRAC cluster. The OCFS was first brought to market in August, 2001, as an innovation that allowed commodity x86-based servers to leverage a global file system without having to access the server operating systems that were running on those servers. It also allows individual servers in the clusters to have unrestricted access to all of the files in the cluster — without having to allocate specific segments of disk-storage to each physical server before the clustering takes place. ©2003 IDC #3814 7
The OCFS software was originally written to provide a single, global pool of files to all of the servers attached to a single Microsoft Windows 2000 cluster running the Oracle database. This technology, when enabled on Linux fail-over clusters based on Oracle's 9i RAC parallel database technology, opened the door to the open-source community development process and, importantly, provided a path for Linux to move to high-value workloads. Today, many leading-edge users are deploying Linux clusters to run commercial workloads on Oracle 9iRAC parallel-database server solutions. Although Oracle has this "early mover" status in "scale-out" clustered- server deployments, it is a building block for many types of server solutions that will be delivered on top of the Oracle database engine itself. ROI TOOLS, CASE STUDIES AND BEST PRACTICES Dell offers ROI tools that allow IT managers and senior business management to evaluate Linux servers as platforms for HPC or commercial workloads. These ROI tools allow each IT shop to enter data specific to the enterprise or organization — and to calculate the pay-back period from a future investment in Linux server technology. Through a combination of tools based and consultative discovery and analysis, Dell Professional Services has built considerable expertise in assisting clients migrate and consolidate their IT infrastructure to industry standard x86 server platforms and open Linux operating environments. DELL CUSTOMERS ARE ADOPTING LINUX SERVER SOLUTIONS Last year, IDC reported that Dell shipped more than 117,000 Linux servers worldwide. Many of these Linux servers went to large enterprises that are migrating and consolidating their IT infrastructure around industry-standard and open-source server solutions to reduce costs and to create a more profitable technology foundation for their business. One of the most prominent customers that have turned to Dell for help was the Center of Excellence in Bioinformatics at the State University of New York at Buffalo, which purchased 2,000 Dell PowerEdge 1650 and 2650 Red Hat Linux-based servers as part of a high performance computing (HPC) cluster. Leading companies that have installed Linux clusters from Dell include Toyota, Saudi Aramco, and CBS. In 2003, IDC estimates that nearly 800,000 Linux servers will be sold worldwide, making the Linux server market segment one of the most significant opportunities in the server market and clearly demonstrating customer demand for this platform to enable better technology and business integration. Dell is well positioned to be one of the market leaders in this market segment, based on its ability to help customers make the transition from Unix server to Linux servers ― and to consolidate their infrastructure around this maturing server solution. H O W D E L L S E R V I C E S P R O V I D E A C O M P L E T E L I N U X S E R V E R S O L U T I O N Dell has built a number of programs to enable a more seamless migration and consolidation to Linux-based server solutions. Dell customers have the flexibility to purchase everything from configure-to-order rack-optimized PowerEdge Dell servers to in-depth professional services engagement to help customers integrate Linux solutions in their data center. Dell also offers a "Fast Track to Linux" offering to help customers through this process. Each Fast Track migration service consists of a four week program that helps customers determine the feasibility and potential benefits associated with a migration to a Linux-based server solution. Fast Track to Linux is a Dell professional services engagement targeted at understanding customer migration strategies within four server workload categories: 1) Web applications; 2) Java; 3) C/C++ custom applications; and 4) Oracle databases with Red Hat Advanced Server. Dell has also made a Linux environment easier to deploy and manage. The company has made considerable investment in Dell's OpenManage server administrator to 8 #3814 ©2003 IDC
enable the management of PowerEdge servers both remotely through a web browser or directly at the server. This capability is especially critical in data center environments that have hundreds of Linux servers that need to be managed, maintained and upgraded. Dell's ability to help customers deploy and to manage Linux server solutions is one of the key attributes of the vendor and is a high priority among many of the company's larger clients. Indeed, the ability to manage a scale-out clustered server configuration is key to its success as a platform for enterprise computing. IDC research has found that one of the top historical reasons for user dissatisfaction with clustering is when deployments are not easy to deploy or to operate, on an ongoing basis, or when software is difficult or costly to use. Therefore, Dell must work closely together with its ISV partners, like Oracle, to ensure that there system management software is easy to deploy and to use. Further, easy-to-use system management software will also help to keep IT administration costs under control. CHALLENGES AND OPPORTUNITIES Dell's greatest challenge in its plan to move customers from traditional Unix/RISC servers to Linux "scale-out" clusters will be to prove that there is adequate functionality and scalability in its solution, and that there is enough return on the costs associated with such a move. Dell is already working closely with Oracle to optimize the Oracle 9iRAC clusters that are built on top of Dell servers, the Oracle 9i database, and Red Hat Linux. But this is an ecosystem play, and one that Dell cannot undertake unilaterally. The company is working with a collection of partner vendors, to develop a complete ecosystem. Of course, Dell's competitors, HP and IBM in particular, both are working to develop their own ecosystem aboard Linux. Dell's Unix/RISC server competitors are known for their focus on optimizing specific hardware/software combinations to boost overall system performance and reliability — by tuning system software to hardware, and by working closely with ISV partners, including database companies. In addition, while Dell leads in U.S. Linux server sales, it is not the worldwide Linux server leader. The company's chief competitors, IBM and HP, have developed strong relationships and a significant channel and sales force in regions out side o the U.S. which Dell will have to overcome. Strengthening its international sales represents a challenge as well as a growth opportunity for Dell. Dell also faces the task of transforming its early success in high-performance computing (HPC) clusters, built on top of dozens, or even hundreds, of Dell servers into a success in the commercial enterprise space. In this commercial world, Dell will have to convince longtime practitioners of scalable Unix/RISC technology that "scale- out" clustering can be as effective as "scale-up" database serving. That task was somewhat easier in the HPC space — where workload-balancing clusters divided up the total workload — and assigned pieces of that workload to specific servers within the cluster. But Dell can make good progress if it continues to work closely with Oracle, if it builds on the successes of early adopters — and if it boosts the number of server nodes that can be included in an Oracle 9iRAC Linux cluster beyond the current six to eight server nodes. Compared with Unix servers, Linux servers are not yet widely deployed for intensive business processing, online transaction processing (OLTP) and decision-support workloads. The ecosystem developed around scalable UNIX/RISC servers to run high-end enterprise workloads and large databases has taken years to mature. Linux and Intel-based servers are beginning to take on these workloads, but IDC expects it ©2003 IDC #3814 9
will take several years for the entire Linux ecosystem for commercial applications and databases of this scale to mature. However, some commercial workloads such as collaborative computing (including email); file/print workloads; Web workloads and business workloads supported by ISV applications (i.e. ERP), are already available in the Linux server environment, in addition to a wide variety of HPC workloads (including many that are supported by Beowulf clustering and workload-balancing software). IDC is confident that commercial workloads will become more commonplace on Linux servers, over time, although it may take some time to develop feature/functions in Linux that are absolutely equivalent to those developed for the Unix operating system over a period of many years. The other key consideration is return on investment. Since a movement from one architecture to an alternative architecture costs real dollars, real staff hours and carries some potential risk, customers need to justify the return that they will receive in a move from Unix/RISC systems to a Linux/IA solution. While acquisition cost of new system configurations might be a critical consideration, customers will also need to evaluate related reductions (or lack of reductions) in acquisition, maintenance or upgrade costs. IDC believes another key consideration is a company's architectural roadmap, and what future requirements may be driving a company's IT investment strategy. The software services and hardware capabilities that are needed this year, next year, and beyond, will heavily influence investments made today. CONCLUSION Dell has made a convincing case that customers can approach commercial workloads, especially those that depend on database updates, by "scaling out" rather than "scaling up" with traditional scalable server solutions. Its close working partnership with Oracle, which is centered on the Oracle 9iRAC technology running on Linux servers, is gaining some important supporters across the Linux ecosystem, and among some early adopters in the IT community. These combinations of enterprise-class products from technology leaders in the industry have convinced some customers to adopt Linux servers for HPC and for commercial applications. They see it as part of a larger strategy to standardize on fewer hardware platforms within their data centers, and as a move that has the potential to reduce acquisition costs for hardware and software—as well as to reduce their IT personnel costs by simplifying system administration. There are, indeed, savings to be made and costs to be reduced in the acquisition phase of deploying a Dell Linux cluster running Oracle 9iRAC, compared with multi- million-dollar scalable database solutions. However, the larger question, which Dell must answer for IT managers, is whether this scale-out solution can do as much, and be as reliable, as earlier combat-tested scalable Unix servers running database engines and database applications. Thus, the real contest in the marketplace will be one over total cost of ownership (TCO) rather than one over initial purchase price and proving that the scale-out Linux cluster solution will save IT shops money over their planning horizon of three to five years. This is an important question, since scalable midrange and high-end servers tend to have a useful lifetime of five to seven years, or more. If Dell can prove that it is leveraging a technology whose day has arrived, and that it is capitalizing on a trend to modular computing technology and virtualization that is all but inevitable, then it will have played a role in gaining IT acceptance for Linux server clusters as a mainstream play in the worldwide server market. 10 #3814 ©2003 IDC
B E N E F I T S O F L I N U X M I G R A T I O N FLEXIBILITY IN DEPLOYMENT Linux server clusters lend themselves to flexible deployment. This is because IT managers can add server nodes, over time, as computing requirements grow, and as the number of end-users to be supported grows. Leveraging the ability to add server nodes, IT managers can handle capacity planning, and capacity expansion, in a more granular fashion than in possible when deploying "scale-up" symmetrical multiprocessing (SMP) servers that have many processors in a single computer cabinet. Likewise, Linux server clusters can be "re-sized" by removing servers from the cluster, if demand for computing resources subsides. Here, system management capability is of high importance, as accurate monitoring of computing activity will help system administrators to "dial up" and "dial back" on clustered systems, as needed. HIGH AVAILABILITY Linux server users have been surprisingly confident in the capabilities of Linux. In a study conducted in 2001 prior to the launch of products including the 2.4 kernel, IDC found that users rated Linux reliability on a par with commercial Unix distributions, and operating systems quality just below that of commercial Unix versions. In a follow-up study conducted in late 2002, we again found that Linux was often treated as a peer to Unix products for specific workloads. Obtaining high levels of availability often is made possible by cluster-ready technologies, including shared file systems, interconnects and software that enables the sharing of storage elements. Clustering and high availability software are part of a larger category of products that IDC calls serverware. This technology is typically sold as independent system software that extends, coordinates, or "virtualizes" the resources provided by interconnected servers or nodes, regardless of their underlying processor architecture or operating system. It is often sold separately from the operating system upon which it runs. PERFORMANCE AND SCALABILITY Prior to the release of the 2.4 kernel in 2001, Linux was bound by performance limitations when scaling up past two processors. Today, the Linux 2.4 kernel is considered to be mature and stable, and it has proven itself to offer good performance and scalability in uniprocessor, two-way and four-way configurations. While proponents cite the 2.4 kernel as offering good performance on 8-way SMP hardware, this is a configuration that is rarely seen in Linux systems, to date. Additionally, systems vendors are exploring ways to gain system scalability through "scale-out" clustering technology. If globally shared file servers can be combined with fast interconnects and parallel databases, such as Oracle 9i or IBM DB2, then "scale- out" Linux clusters can begin to take on workloads that formerly were directed to scalable SMP Unix servers to support equivalent computing tasks. I M P O R T A N T P O I N T S T O C O N S I D E R B E F O R E M I G R A T I N G Prior to undertaking a migration from Unix to Linux, IDC advises users to consider the following issues: ! Application compatibility. While Linux has considerable similarities to Unix, and application portfolios can be ported from one environment to the other, not all commercial vendors offer versions of their product that are intended for deployment on Linux servers. ©2003 IDC #3814 11
! Middleware availability. Any applications that require underlying infrastructure such as transaction processing capabilities, application serving, storage or other resource virtualization software, and distributed file systems must be available, and be compatible with the application products. ! Absolute scalability. While Linux offers good scalability to 4-way servers and in some workloads, 8-way servers, this environment is not considered to be a candidate for more highly scalable workloads. If application requirements demand higher levels of scalability, Linux may not be the best choice for production commercial systems today. This is subject to change, of course, with the version 2.5 development kernel (which will enter the market as version 2.6).While predicting the specific release schedule of upgrades to the Linux kernel can be difficult, the general consensus is that the 2.6 kernel will be locked down and made available no sooner than the second half of 2003, and could drag into 2004. T H E M E C H A N I C S O F M I G R A T I O N If an IT shop is serious about migrating existing Unix applications to Linux applications, several approaches can be taken: ! Replacing the existing Unix system and packaged applications with a new Linux server and packaged applications. This is the easiest and most straightforward way to move from one system to another, providing equivalent functionality can be found in the replacement Linux server system and associated system software. ! Modifying the packaged or custom Unix application to run under a Linux distribution. In this case, the code will need to be "check-pointed" to spot code that was written to specific application programming interfaces (APIs) of major brands of Unix, including Sun Solaris, HP HP-UX and IBM AIX that might not be supported by Linux. If dependencies are found to brand-specific APIs, those must be addressed through rewriting. ! Providing no major dependencies are found to a specific "flavor" or brand of Unix, recompiling an application that was originally written to run on a Unix/RISC platform to run on a Linux/x86 platform. Users must recognize that many applications originally written to run on Unix servers can be moved, sometimes without major change, to Linux platforms. But care must be taken to carefully screen and evaluate those Unix applications, to identify areas of code that must be modified, revised, or recompiled to run on Linux/x86 platforms. C O P Y R I G H T N O T I C E External Publication of IDC Information and Data — Any IDC information that is to be used in advertising, press releases, or promotional materials requires prior written approval from the appropriate IDC Vice President or Country Manager. A draft of the proposed document should accompany any such request. IDC reserves the right to deny approval of external usage for any reason. Copyright 2003 IDC. Reproduction without written permission is completely forbidden. 12 #3814 ©2003 IDC
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