Mainframe computer

Mainframes (often colloquially referred to as big iron) are large and "expensive" computers used mainly by government institutions and large companies for mission critical applications, typically bulk data processing such as censuses, industry/consumer statistics, ERP, and financial transaction processing.

Market context

Nearly all mainframes have the ability to run (or "host") multiple operating systems and thereby operate not as a single computer but as a number of "virtual machines." In this role, a single mainframe can replace dozens or even hundreds of smaller servers, reducing management and administrative costs while providing greatly improved scalability and reliability. The reliability is improved because of the hardware redundancy noted above, and the scalability is achieved because hardware resources can be reallocated among the "virtual machines" as needed out of total system capacity. Mainframes can add system capacity nondisruptively, instantly, and granularly — what IBM marketing, with justification, describes as "on demand computing." Modern mainframes, notably the zSeries and System z9 servers, offer at least three major levels of virtualization: logical partitions (LPARs, via PR/SM), virtual machines (primarily via z/VM), and the protected and virtual addressing and workload management of their operating systems, notably z/OS. Together, these virtualization technologies support business-friendly mixed workloads, including Linux and Java, in a highly reliable and efficient manner.

Related Topics:
Virtual machine - IBM - ZSeries - System z9 - Virtualization - LPAR - PR/SM - Z/VM - Z/OS - Mixed workload - Linux - Java

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Whether the acquisition cost of a mainframe makes sense will depend on its return on investment (ROI). Mainframe ROI, like any other computing platform, is dependent on its ability to scale, support mixed workloads, reduce labor costs, deliver uninterrupted service for critical business applications, and several other risk-adjusted cost factors. Some argue that the modern mainframe is not cost-effective. Sun, Hewlett-Packard, and Dell understandably take that view, and so do some independent analysts. However, in recent years the majority view is that mainframes are uniquely valuable (and cost-effective) for many businesses and governments. IBM's zSeries and System z9 revenues are growing, despite declining prices, suggesting that view is indeed widespread among technology buyers. Major independent analysts, such as Gartner, reinforce that assessment.

Related Topics:
Sun - Hewlett-Packard - Dell - ZSeries - System z9 - Gartner

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There's no question that mid-tier servers are improving. Logical partitioning, at least in basic form, is now found in many high-end UNIX-based servers. However, all servers are improving, not just non-mainframe servers. For example, zSeries/z9 servers execute each instruction twice, compare results, and shift workloads "in flight" to functioning processors, including spares, without any impact to applications or users. This rare feature, also found in Tandem Computers, is known as lock-stepping, because both processors take their "steps" (i.e. instructions) together. Not all applications absolutely need the assured integrity that these systems provide, but many do, such as financial transaction processing.

Related Topics:
UNIX - Tandem Computers

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Undoubtedly debates will continue about the mainframe's value — and, for that matter, about the value of other computing platforms, such as the PC. The debate began with the 1964 introduction of the IBM System/360 and has continued for over 40 years.

Related Topics:
PC - 1964 - System/360

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As of early 2005, IBM mainframes dominate the market at over 90% marketshare. Unisys still manufactures ClearPath mainframes, based on earlier Sperry and Burroughs product lines. Fujitsu is nominally still in the market, servicing machines based on the former Siemens and Amdahl lines, while Hitachi has left the mainframe business (except for the zSeries 800 jointly designed with IBM). Bull's DPS mainframes are still on the European market. Acquisition costs vary, but new IBM mainframes start "under $200,000" (zSeries 890 Model 110, U.S. 2005 reported price, excluding disk storage).

Related Topics:
2005 - IBM mainframe - Unisys - Sperry - Burroughs - Fujitsu - Siemens - Amdahl - Hitachi - ZSeries - Bull

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