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PAI/O Driver for z/OS Overview

The DASD­ Dile­mma

Today, z/OS installations face the need to make some of the most significant DASD acquisition decisions that they have ever made. After more than three decades of acquiring large form factor DASD devices specifically designed for mainframe systems, you now face a bewildering array of alternatives.

These range from RAID to log-structured file schemes, all of which promise enhanced performance and fault tolerance. Rather than being traditional mainframe disks, new DASD subsystems are composed of small form factor commodity disk devices which have historically been employed in personal computers and workstations.

To further complicate the decision process, the performance claims made for these DASD subsystems strain credulity as never before. As a potential buyer, you often find almost an order-of-magnitude difference in the performance characteristics of a prospective DASD subsystem when you compare the claims of the vendor, the critical observations made by competitors, and the informed opinions of industry pundits, many of whom simply estimate DASD performance by talking to the vendors. Moreover, the use of analytic models to analyze the potential performance of new technologies is complicated by the vendors' increasingly secretive stance in regards to providing information about the internal structure and algorithms employed by their subsystems. As a result of these factors, many installations are approaching some of the largest storage acquisitions in their history without a reliable basis for understanding the true capabilities of the new technologies.

The PAI/O Driver Solution

PAI/O Driver for z/OS
from Performance Associates is the solution to this dilemma. Our product is both technology independent and vendor independent, and it comprises four distinct parts:

­Installations can employ PAI/O Driver for z/OS to help in the DASD selection process, to aggressively negotiate acquisition agreements, or to verify performance clauses in DASD acquisition contracts. It can:

When you have PAI/O Driver for z/OS, you can tell the vendors what you want and verify that you've gotten it!

The DASD Acquisition Methodology

A library of profiles for the most current DASD subsystems is included with our user enterprise-licenses. An inventory of our profile library is maintained on our home page at

The Reporting Service

In contrast to marketing claims about DASD subsystem performance, the PAI/O Driver for z/OS reporting service presents and interprets hard repeatable DASD subsystem performance measurements. Rather than being a benchmark of a particular workload, PAI/O Driver for z/OS employs a specifically designed standard engineering test series to explore the performance characteristics of any DASD subsystem over a wide variety of configuration alternatives and workload types.

While there is no single test which can provide an absolute evaluation of the suitability of a DASD subsystem for a specific workload or customer environment, each
PAI/O Driver for z/OS subsystem profile report provides your installation with reliable commentary and analysis. This is because it is based on hard measurement data, not unsubstantiated marketing claims or industry hearsay.

We at Performance Associates are committed to the continued measurement and analysis of new DASD subsystem offerings and the publication of our research reports to licensed user sites. While we will formally distribute new subsystem profiles to subscribers on a semiannual basis, we will make informal results available as soon as they are collected.

In the event that you have installed, or have access to, a subsystem which has not yet been analyzed, we will perform the analysis at our own expense.

The Software

PAI/O Driver for z/OS is compatible with MVS/ESA 4.1 through the most current releases of z/OS and is Year 2000 compliant. It features a standard engineering test series and includes SAS® workload profiling software for the development of customer-specific performance verification tests.

Performance Associates Services

We can assist you in the measurement, analysis, and acquisition of new DASD subsystems or unique configurations. Being well versed in the specific requirements presented by state and federal acquisition regulations, we can help speed the acquisition process for government agencies and certify the performance of upgrades over the life of your contract.

Licensed DASD Vendors

Recognizing the value of PAI/O Driver for z/OS for independent performance testing of new DASD subsystems, all major DASD vendors and manufacturers employ it as a supplement to their own internal vendor-specific performance tests.

­Licensing and Additional Information

PAI/O Driver for z/OS is an enterprise-licensed product. For additional information and license terms, please contact Performance Associates at:

Performance Associates, Inc.
P.O. Box 5080
Pagosa Springs, CO 81147-5080
Voice: (970) 731-DASD x104
Fax: (970) 731-1024