LINUX for S/390 Strategy

May 2000

Executive Summary

Growth of the Internet is enabled by standards, and IBM is seriously committed to open standards. LINUX® [ http://www.s390.ibm.com/linux/ ] is the pervasive open system standard, as such Linux is the fastest growing server operating system. It is most popular in small to midsize Intel-based PC servers. It has become a rallying point within the industry, one that will play a key role in the evolution of the next generation of e-business networks and computing. Linux is more than just another operating system. It is the product of an ongoing collaboration among the best programmers in the industry coming together to create an operating system that can work on a variety of hardware platforms.

Linux has been quite popular as the operating system for web servers, file and print servers, and various Internet access infrastructure servers, both in enterprises and in the NetGen marketplace. It is, however, on a path to becoming a viable enterprise operating system, capable of running a variety of workloads requiring high scalability and industrial strength. IBM® is an ongoing contributor to the Linux community, helping to enhance Linux's capabilities as an operating system for e-business

Linux runs natively on S/390® and Linux applications that run on other hardware can be recompiled to run on S/390 Linux. As with other S/390 operating systems, customers have the flexibility of running Linux in a dedicated S/390, or they can run multiple images of Linux on a single S/390 as virtual servers, using either logical partitions (LPARs) or VM/ESA®. No other hardware platform can offer customers the flexibility of deploying hundreds of Linux images on a single machine. This flexibility enables customers to benefit from reduced operational costs through centralization of backup and recovery and other administrative tasks.

Businesses have many server platforms from which to choose. Each server platform offers businesses a different style of computing to meet their needs. Businesses will evaluate a number of factors when selecting a hardware platform.

S/390 is well positioned to take advantage of growth in the Linux market. S/390 is the industry's most reliable hardware platform. Its self-configuring and self-healing attributes such as CPU and memory sparing, fault-tolerant cache structure, and transient error recovery have made S/390 reliability legendary. While the reliability of Linux as an operating system may be similar across server platforms, S/390 architecture will put applications running on Linux one step higher in availability.

The value of S/390 and Linux is:

The Linux application portfolio will greatly increase the number of applications available to the s/390 customer
All of the great flexibility and openness of Linux combined with the qualities of service of S/390 results in an industrial strength Linux environment
S/390 can uniquely provide customers with the ability to consolidate a large number of servers onto a single platform easily, a "server farm in a box".
Customers can blend the data richness of the S/390 environments with the Web capability of Linux applications to deliver a highly integrated e-business solution

Why Linux and why Open Source?

The evolution of e-business is presenting customers with a new set of challenges:

Integrating multiple applications and databases across a spectrum of operating systems, running on multiple servers, each with unique management requirements, distributed geographically, and crossing company borders.
Responding to the business impacts of delivering performance and high availability in environments where peak demands and business growth may be difficult to predict and there are substantial demand spikes.
Providing floor space to house a large number of servers.

One major factor in a customers' choices of hardware and software platforms is application availability. Where an application can be hosted on multiple platforms, they select a platform based on analysis of numerous factors, such as:

Existing platform infrastructure
In-house expertise
Price/performance
Availability/reliability
Long-term cost of ownership
Training costs
Administrators, support, users...
Service and support
Market future of platform

When they outgrow the capabilities of their current platforms, implementing changes necessary to grow can be extremely disruptive to their businesses. Linux is more than just another operating system. It is the product of an ongoing collaboration among the best programmers in the industry coming together to create an operating system that can work on a variety of hardware platforms.

Linux is becoming a rallying point within the industry, one that plays a key role in the evolution of the next generation of e-business networks and computing. Linux is more than just another operating system. It is the product of an ongoing collaboration of the best programmers in the industry coming together to create an operating system that can work on a variety of hardware platforms.

Linux is already the fastest growing server operating system. Linux today is most popular on small to midsize Intel-based PC servers, as well as on clusters of such servers. It is very popular as a platform for modest-sized Web and e-commerce servers, ISP/ASP applications, dedicated networking functions (such as Web-infrastructure, file/print, LAN, firewall, DNS, e-mail, and so on), supercomputing clusters, as an embedded operating system for new server and client application appliances, as well as the development platform for many innovative "next generation" applications. As the robustness and capabilities of Linux are enhanced, there is a growing need for a larger-scale, more cost-effective hardware platform that can host multiple enterprise-focused Linux applications.

As a technology, Linux is developing into one of the standard development platforms for the spectrum of applications that comprise our customers' e-business solutions. Linux provides consistent operating system services across all open platforms so application can be rehosted quickly. IBM's Application Framework for e-business allows you to port applications quickly. Together they make application mobility a reality by creating an environment where applications are developed once and with minimal effort can be deployed across a broad range of servers and environments. This application mobility is essential for customers to be able to respond quickly to the dynamic nature of e-business.

The impact of Linux is that customers will be able to select independently: 1) the applications that are best suited to their business needs, 2) hardware platforms matched to their quality of service (QOS), performance and capacity requirements and 3) operating environments that impart critical characteristics to the applications. Linux is on a path to becoming a viable enterprise operating system, capable of running a variety of workloads requiring high scalability and industrial strength. IBM® is an ongoing contributor to the Linux community, helping to enhance Linux's capabilities as an operating system for e-business

Why Linux for S/390?

The Linux application portfolio will greatly increase the number of current applications available to the S/390 customer, a significant enhancement. Besides that, all of the great flexibility and openness of Linux combined with the qualities of service of S/390 results in an industrial strength Linux environment. In addition, S/390 can uniquely provide customers with the ability to consolidate a large number of servers onto a single platform easily, a "Server Farm in a Box". Also, Customers can blend the data richness of the S/390 environments with the Web capability of Linux applications to deliver a highly integrated e-business solution.

Linux offers S/390 a truly portable application environment. By using the identical source code on all platforms, a simple recompile is generally all that is required to rehost an application. S/390 is the only platform that provides the flexibility of deploying hundreds of Linux images and applications on a single S/390. These applications will benefit from the robust availability characteristics built into S/390 hardware. For e-business applications, higher availability translates directly into continuing business operation. The term availability is often abused, as every advertisement discussing an operating system uses it. Hardware that adds availability to an application must have self-healing attributes to protect an application from failure. These include computational integrity, fault tolerant cache hierarchy, transient error recovery, memory chip sparing, CPU sparing, zero outage hardware repair, and concurrent microcode updates.

No other platform can recover from failure without impact to the application as well as S/390.

Linux for S/390 or Linux on other platforms?

There are three distinct classes of servers:

Data Transaction Servers — high-speed transaction and database servers
Web-application servers — these servers enable rapid application deployment
Special Function Servers — these servers enable manageable network infrastructure

The first enables the rapid deployment of applications, such as e-business front-end applications. The second enables a manageable network infrastructure capable of tying the front end servers to LANs, WANs, the Internet and high speed access with the third class, namely the high speed transaction and database servers. As applications encompassing all three server classes began appearing, customers began analyzing the best platform for their needs. With the advent of Linux, customers may soon be faced with this analysis for most of their application needs.

So let's review the factors considered in choosing a platform and discuss each in detail.

Existing platform infrastructure
If a customer already has a mature infrastructure in place, than using existing capacity, or adding incremental capacity will likely prove the cost-effective method of deploying an application. Customers evaluating existing platforms will also look at the long-term cost of ownership as well as the other factors to ensure their existing platform is the correct match for their needs.
In-house expertise
In-house expertise includes items such as a help desk, systems management, database administration, application development, capacity planning, and availability management. These are all critical to meeting service level objectives. If a customer already has expertise on a platform that has proven effective in these areas, it is risky and expensive to change platforms and rebuild this expertise.
Price/performance
Price/performance involves the initial cost of the total infrastructure. Many customers use this up-front cost along with other factors, especially the long-term cost of ownership, to understand the overall effect on their ongoing IT expenditures.
Availability/reliability
Reliability defines how often the hardware and software run into problems. It is generally measured in mean time between failures (MTBF). Availability defines how much time the application is available to end users. Applications running on a high-availability hardware architecture such as S/390 can isolate and recover from many hardware and software failures, ensuring the availability of the application to the end user. Mission critical applications generally demand the best availability.
Long-term cost of ownership
Long-term cost of ownership involves the total up-front and operational costs of the solution. It includes the hardware, network, software, maintenance, services, energy, and labor required to keep the application operational. It is generally calculated over three to five years and is translated into cost-per-user-month or cost-per-transaction.
Training costs
Training costs are the costs required to educate staff to deploy the application. Any platform-unique education can cross into help desk education, as well as systems and network administration.
Administrators, support, users
This involves those people who administer or support the infrastructure. Customers tend to favor platforms for which they have, or can easily acquire, the skills, and that will not increase their costs for administration or support staff. Likewise, any platform change that will directly affect the customers end-user will be avoided.
Service and support
The level of service and support of the platform is often a deciding factor when a mission critical application is involved. Service and support include the defect support available and the reputation of the provider, as well as availability of resources for assistance with general technical questions. Oftentimes, peers in other companies, user groups, and Internet-based forums serve as valuable additional support channels.
Market future of platform
The perceived future of the platform will of course guide a customer platform decision, as well as determine the up-front expenditures the customer is willing to risk.

Net: Customers must evaluate multiple factors to choose the platform that best meets their needs. These factors, when taken together, reflect the total cost of ownership and speed of deployment.

When OS/390 and when Linux for S/390?

As one analyst points out: "S/390 reliability is legendary, and dramatically better than can be achieved with most other systems". This reputation was not achieved by accident. IBM has developed the S/390 architecture and OS/390 operating system to run the world's most critical applications at availability levels reaching 99.999%. IBM will continue its investment in OS/390, bringing robustness and qualities of service into new interfaces and programming models. OS/390 became one of the first UNIX-branded operating systems. The UNIX® support in OS/390 has evolved into a robust UNIX application hosting environment, bringing S/390 qualities of service to important UNIX applications and middleware.

Applications and middleware ported to the OS/390 environment generally require tuning and optimization to gain optimal performance and availability characteristics expected with the highest enterprise-class qualities of service. While UNIX applications are portable to the OS/390 environment, the tuning and optimization requirement may add a level of expense which may not be necessary if it doesn't need the same mission critical qualities of service. However, e-business applications have a strong requirement for high-speed access to data residing on OS/390 transaction and database systems. Linux will complement OS/390 to meet this need.

Most e-business solutions run a two-tier architecture, namely a highly mission-critical transaction and database tier, and a highly flexible web front-end tier. OS/390 is clearly the leading platform for the transaction and database tier, and it integrates with the Web tiers in three main ways:

Distributed connections: Where the Web function is distributed in the network, connected to OS/390 using networking protocols and networking bandwidths.
Glass house connections: Where the Web function co-resides in the "glass house" with OS/390, which enables much higher bandwidths as well as higher degrees of integration, for example, common systems management.
Inter-platform connections: Where Web functions now run on Linux® for S/390® in an LPAR or a virtual machine, communicating with OS/390 at very high bandwidths. These will soon approach memory bus bandwidths.

A single S/390 machine running OS/390 in one partition with Linux in another combines the robustness of OS/390 middleware with the rich supply of Linux applications.

Net: Linux complements OS/390 enabling rapid Web application deployment while providing rapid access to DB2, IMS, and CICS.

Linux for S/390: Virtual Servers or Native?

Whether connecting to back-end data or consolidating scores of servers, S/390 partitioning offers customers the greatest degree of flexibility. One option is to run Linux as a virtual machine using VM/ESA. VM provides virtualization of CPU processors, I/O subsystems, and memory.

A customer running VM can have hundreds of Linux systems running on a single S/390. With VM, a customer can offer a complete Linux server environment to each of their application developers and host production systems all on the same S/390 machine. Other benefits of this hosting are:

VM can provide very high-speed connections (currently up to 350 Mbytes per second) among Linux systems and other S/390 resources.
VM allows for virtual networks so that many logical networks can be built using one physical network connection with simplified configuration planning.
VM provides enhanced device support, such as virtual disks and peer-to-peer remote copy, for Linux systems.
Customers can use VM backup facilities to back up all Linux data. This means you can have a single backup solution for all Linux servers.

For many S/390 customers, running Linux in a logical partition (LPAR) is an option. The S/390 hardware can be logically partitioned into a maximum of 15 separate LPARs. A single S/390 can host OS/390 applications in one partition, VM and VSE applications in others, and Linux applications in additional ones. LPARs offer customers access to legacy data through a high-speed channel-to-channel (CTC) network, avoiding additional LAN network traffic. Data transfer across a logical partition, using CTC, eliminates the network complexity providing for higher availability and faster, more consistent end-user response time.

And of course, a customer could run a single Linux operating system on the S/390. This means Linux will have complete control of the entire S/390. However, running natively does not provide the flexibility to add Linux systems for testing or additional applications.

Net: S/390 is the most reliable and the most flexible hardware platform available. Customers can run from one to hundreds of Linux servers on a single S/390.

LINUX for S/390 home [ http://www.s390.ibm.com/linux/ ]

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Printed in the United States of America, May 2000
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