This makes the AS/400 DASD market look like a busy intersection with a car dealer on each corner. The only problem is that all the cars possess nearly identical features and price tags. Imagine the kind of competition such a situation would create and you will understand the midrange storage world. It is the ultimate buyers' market, a place where the discriminating customer can realize substantial savings.

If you want a refresher on storage solutions before attacking the market, this buyer's guide gives you the background you need to negotiate the right purchase. The article begins with an explanation of AS/400 storage concepts that have affected the strategies of vendors who sell DASD to 9406 sites. Next, it outlines the major market trends and examines the strategies of the six major vendors. Finally, the article provides you with some strategies to obtain the right storage solution at the lowest possible price. The buyer's guide is limited to 9406 DASD because most vendors have not developed products for the 9402 and 9404 markets. We've provided information about the emerging 9404 DASD market in the "A Word About 9404 DASD" sidebar.

AS/400 Storage...A Quick History

Ever since the AS/400's introduction, the one factor that has driven midrange DASD evolution is the system's unique storage architecture. At the heart of that architecture is the concept of single-level storage. In the simplest of terms, single-level storage lets the AS/400 see memory and DASD as one large address space. It also lets the system automatically place objects in memory or DASD and assign addresses to those objects.

This ability is both a blessing and a curse. On the positive side, programmers do not need to reserve space for an object. On the negative side, automatic allocation can spread objects across several disk drives. If one of these drives breaks down, virtually all objects become unusable because they lack some fragment.

In the not-so-distant past, such an event usually forced an AS/400 site to take the system offline and restore it entirely from a tape backup. Because this is a time-consuming process, IBM introduced data-protection methods such as checksum and disk mirroring to speed up or eliminate the restoration process. (Each boldfaced item is defined in the glossary on page 46.) The problem with these data-protection schemes is that they degrade system performance or require additional disk resources. As a result, only 10-20 percent of all sites use these methods for every disk drive.

In response to these problems, IBM and its competitors developed less onerous methods to protect data and increase system availability. These include dynamic spare disks, redundant components and controller microcode that detects failing sectors or drives and rewrites data to vacant drive sectors or dynamic spare disks. Vendors also improved the reliability of their drives by boosting mean times between failure (MTBF).

In 1992, XL/Datacomp and IBM introduced another protection scheme known as redundant arrays of inexpensive disks, or RAID. While several types of RAID protection schemes exist (including disk mirroring, otherwise known as RAID1), the acronym is most commonly associated with RAID5 arrays. These arrays stripe parity information across a group of drives in much the same way as IBM's checksum facility. Unlike checksum, the arrays' controllers maintain the parity information instead of the AS/400's CPU. This reduces system overhead and enhances performance.

Midrange DASD vendors have also improved the performance and pricing of their products along with their reliability. They have achieved rapid performance gains through seek time reductions, data transfer rate increases, and larger controller buffers and caches. Increasingly, however, it is the intelligence within disk controllers that determines storage performance rather than the hardware itself. As for pricing, vendors have made tremendous reductions in the cost per megabyte (MB) of storage through increased aereal densities and improved production processes.

Trends in the DASD Market

All these vendor strategies are spurring a massive change within the AS/400 DASD market. As I see it, five major changes are taking place.

1. The storage market is breaking down into distinct segments based on the level of data protection. Until late 1992, almost all AS/400 DASD offered similar levels of data protection because they lacked built-in protection capabilities. Over the last year, the market has split into several levels as vendors have added RAID5 to their product lines. The market now consists of five distinct segments, as shown in 1.

1. The storage market is breaking down into distinct segments based on the level of data protection. Until late 1992, almost all AS/400 DASD offered similar levels of data protection because they lacked built-in protection capabilities. Over the last year, the market has split into several levels as vendors have added RAID5 to their product lines. The market now consists of five distinct segments, as shown in Figure 1.

2. High-availability DASD is quickly taking market share away from conventional disk arrays. This is largely the result of the cost of high-availability DASD which is approaching that of conventional disk subsystems. For instance, while IBM's non-RAID 9337-040 costs $5.92 per MB on a list-price basis, its RAID5 9337-240 costs $6.77 per MB, or only 14 percent more.

This narrowing price gap is changing the trend in storage-system purchases. When IBM first shipped 9337s in the fall of 1992, about one-third of all units shipped had RAID5 capabilities. At present, RAID5 models make up two-thirds of the shipments. As a result, RAID5 drives should continue to make up the majority of DASD purchases at 9406 sites in 1995.

3. High-density, 3.5-inch disks are becoming a commodity item, resulting in rapid price declines and increased market share for vendors other than IBM. Over the last four years, 3.5-inch disks have taken over both the PC and midrange storage markets. Numerous manufacturers now offer disk units that are very similar in terms of storage density, performance, reliability and price. The intense competition between disk vendors has helped cut the cost per MB of storage by nearly 25 percent each year.

During the early 1990s, IBM was slow in its response to this competitive environment. The company continued to sell 5.25-inch disks in its 9336 arrays while competitors were adopting the faster and less expensive 3.5-inch technology. As a result, non-IBM vendors of AS/400 DASD now have close to 10 percent of the DASD market share instead of the 1 percent share they held in 1989.

4. Cache and controller technology is becoming more sophisticated, making physical drive performance less relevant. Not so long ago, the intelligence built into midrange disk controllers was relatively simple and had little effect on DASD performance. As a result, customers could determine the performance of competitive products by comparing physical drive speeds.

Now, most controllers contain read and write caches that run under the direction of sophisticated algorithms. These cached controllers are becoming the primary factor in DASD performance.

This trend, as well as the growing similarity between physical drives, makes it increasingly difficult for one storage vendor to have a clear lead over the others in terms of performance, reliability or price. It also makes traditional performance benchmarks virtually irrelevant. By tuning cache, any vendor can demonstrate a performance advantage for any benchmark.

5. Vendors are using new marketing tactics to secure customer loyalty. Because it is now difficult to achieve clear victories in areas such as performance or price, vendors are looking for new ways to gain leverage. Their most popular tactic to date is to improve the upgradability of their products.

IBM, for instance, offers a field upgrade that transforms non-RAID 9337s into RAID models. IPL has a similar upgrade offering within its ESP 7000 series, and other vendors are joining in with strategies of their own.

The value of this strategy for storage suppliers is clear: it encourages customers to stay with the same company. This type of repeated patronage is becoming increasingly important.

The Vendors...A Closer Look

In addition to upgradability, each vendor is adopting other strategies to cope with an increasingly competitive market. Here's a closer look at the product lines and future plans of the six major vendors. We'll start with IBM because all the vendors must conform to IBM's strategies and the interfaces it supplies on the AS/400.

IBM Corporation-Until late 1992, IBM was a slumbering giant in the AS/400 storage market. Having enjoyed a virtual monopoly since 1988, the company had grown complacent. Then, in response to encroachments from increasingly sophisticated third-party products, the company woke up and struck back with its family of 9337 drives.

The 9337 family comprises a complete line of conventional and high-availability models. Each of the five non-RAID5 models can be upgraded in the field to the 9337-1XX series (RAID5) or the 9337-2XX series (users can switch between conventional and RAID5 modes). Customers can populate each series with one of five different 3.5-inch drives. These drives have densities ranging from 542MB (for high performance) to 1967MB (for high capacity). Models in the 9337-2XX series can connect to IBM's new, high-speed input/output processor (IOP), the 6501, which can transfer data at 20MB per second or four times faster than the 6500 IOP.

IBM will continue improving the 9337 family in terms of capacity and speed. In the summer or early fall, the company will announce new, high-capacity 9337 arrays that use 4GB drives. This will double the maximum capacity of an array to around 27.5GB in RAID5 mode or 31.5GB in conventional mode. While IBM has not set prices for the new drives, early estimates place an array with eight drives at a cost of $5.00 per MB in RAID5 mode and $4.40 per MB in conventional mode. These prices run about 25 percent less on a per-megabyte basis than the lowest price currently available within the 9337 series.

During the first quarter of next year, IBM is likely to announce more 9337 arrays using 2GB drives. While the current 9337-X40 models also use 2GB drives, the drives on the new arrays will have fewer platters than the current design and will rotate faster. This low-profile design provides marginally better performance for customers and a reduced cost of production for IBM.

Decision Data-For years, AS/400 sites have turned to Decision Data for both maintenance services and a variety of midrange peripherals. Last year, however, the company sold its products division to IIS, a peripheral manufacturer located in Israel. In the minds of some customers, Decision Data no longer existed. In reality, IIS continues to actively market products, including DASD, through a subsidiary that bears the Decision Data name. That subsidiary's share of the AS/400 market during 1993 was comparable to those of IPL and Memorex Telex.

Decision Data markets storage arrays that it purchases from EMC. Its 9036 series mirrors EMC's HX3, HX3HA and HX3C lineup and its 9037 models match the HX3SC. While some customers avoid re-labeled products, Decision Data's close relationship with EMC is not necessarily a disadvantage. EMC has a formidable product line and is the leading non-IBM storage vendor. In addition, Decision Data (the IIS subsidiary) provides nationwide maintenance support for its products through an alliance with Decision Data (the service firm). This combination of quality products and service may be the ideal choice for many storage shoppers.

Because of its connection with EMC, Decision Data's future product strategy closely matches that of its partner. The following section reveals where EMC plans to take its DASD lineup.

EMC Corporation-Among AS/400 storage vendors, EMC has sold more megabytes of DASD than any supplier except IBM itself. EMC accomplished this by entering the midrange market early and offering mirrored storage solutions that were often more advanced technically than those of its rival, Big Blue.

EMC offers a full line of Harmonix drives that attach to IBM's 6111 and 6112 IOPs. The HX3 is a high-performance drive that operates in conventional or mirrored modes; the HX3C is a high-capacity, conventional-mode array; and the HX3HA offers EMC's lowest cost per MB for a mirrored array. Last October, EMC also an-nounced its first product that attaches to IBM's SCSI-based 6500 IOP: the HX3SC.

Because of its success with mirrored disk arrays, EMC has been hesitant to move into the world of RAID5. This June, however, it plans to enter that world in grand fashion. At that time, the company will announce a whole new line of RAID5 arrays that will emulate IBM's 9337 series and connect to the 2611, 6500 and 6501 IOPs. The new series will have both high-performance and high-capacity models. In addition, EMC will offer field upgrades from existing HX3 arrays to the new models, primarily through controller swaps.

In a related announcement, the company will demonstrate a software product known as Automated Object Placement. The new product will determine the optimal location for objects-in main memory, controller cache or disk-and instruct the AS/400 to place these objects in the correct area. While controller algorithms improve the performance of the disk arrays they manage, Automated Object Placement will optimize performance across all storage.

Sources within EMC have also indicated that they will match IBM's upcoming announcement of 4GB drives with a 4GB announcement of their own. This announcement could occur a month or two after the IBM models debut.

IPL Systems-Over the last two years, IPL has experienced many changes. In the early 1990s, it sold most of its DASD to resellers, especially XL/Datacomp. After StorageTek acquired XL/Datacomp in 1992 and dropped IPL as a vendor, the company decided to become a direct supplier to customers and started building its own sales force. While this transformation has been rocky at times, IPL's reputation for innovative products is helping the company weather the transition.

A perfect example of IPL's innovation is its ESP 7000 series of upgradable disk arrays. The series starts with the 7637-40, an IBM 9336-compatible array that offers conventional or system-mirrored storage and which customers can upgrade to the 7737 array. The 7737 is a 9337-compatible product that can switch from conventional mode to RAID5 mode. Customers can upgrade their 7737s to IPL's 7037 array, a product that offers the same benefits as the 7737 along with customer-replaceable disk drives and power supplies.

Like IBM's 9337 series, the 7737 and 7037 attach to the 2611 and 6500 IOPs rather than the older 6111 and 6112. To give midrange sites with these older IOPs the benefits of RAID5, IPL also offers the 7036 array. The 7036 attaches to the 6111 and 6112, emulates a 9336 array and can be switched between conventional and RAID5 modes. Customers can upgrade it to a 7037 when they move to a 2611 or 6500 IOP.

IPL fully intends to expand the ESP 7000 series in response to IBM's storage plans. For instance, the company will offer 6501 IOP compatibility on its 7737 and 7037 models by the middle of the second quarter of this year. It will also offer arrays with 4GB drives no more than six months after IBM announces 4GB drives. In addition, the company plans on maintaining a lead over IBM in the area of upgradability. At present, 7737 or 7037 users with 1GB drives can swap the units for 2GB drives, an upgrade IBM does not offer. There is a strong possibility that IPL will also accept current drives in trade for 4GB devices.

Memorex Telex-While Memorex Telex is best known for tape products, it has recently put a greater focus on AS/400 disk arrays. The new emphasis on DASD began last June when the company announced its 3937 array. An IBM 9337- compatible product, the 3937 comes in both conventional and RAID5 models, can contain 1GB or 2GB drives and attaches to 2611 and 6500 IOPs. It also offers several redundant, hot-spare components including disk drives, power supplies, cooling fans and cache memory. The 3937 is currently in beta testing and should ship in April.

For customers who have the 6111 or 6112 IOP, Memorex offers the 3947 disk array. The 3947 is a 9336-compatible series that has both conventional and RAID5 models. While it does not have the redundant components found in the 3937, customers can configure it with a hot-spare disk to allow for immediate rebuilds of data in case of a disk failure. Memorex positions the 3947 as the upgrade path for owners of the older 3936 series. While customers cannot field- upgrade the 3936, the company is giving them financial incentives to migrate.

Like its competitors, Memorex plans to keep current with the latest technology. It expects to announce 4GB drives for the 3937 series no more than two months after IBM announces 4GB drives for its 9337. Memorex will also equip the 3937 with 6501 IOP compatibility by the fall of this year. In short, the company is positioning the 3937 as a product that customers can upgrade with each new technology trend.

XL/Datacomp-Until 1992, XL/Datacomp was primarily known as a reseller. Since StorageTek's 1992 acquisition of XL/Datacomp, the company has become a storage supplier in its own right. In this new role, it is moving aggressively to capture market share with a broad range of products.

The 9638 Northfield disk subsystem is the company's first 9337-compatible storage array. The 9638 is currently shipping with up to seven 1GB or 2GB drives, built-in RAID5 data protection and connectivity to the 2611 or 6500 IOP. By June, XL/Datacomp will ship a microcode upgrade that will let the 9638 hold up to eight drives, switch between conventional and RAID5 modes and attach to the high-speed 6501 IOP.

In addition to the 9638, the company announced a new lineup of 9637 models. The new models emulate IBM's 9337, attach to the 2611 or 6500 IOP and can operate in either conventional or system-mirrored modes. They also serve as upgrade paths for older 9637 arrays. Customers can upgrade any 9637-002 or 9637-003 to a 9637-030 or 9637-040, respectively. Upgrades from a 9637 to a 9638 are not available.

For customers who need fault tolerance as well as RAID5 capabilities, XL/Datacomp continues to offer its Alpine 9600 storage array. The array combines the data-protection features of the 9638 with a wide variety of redundant components including disk drives, controllers and power supplies.

Like other IBM competitors, XL/Datacomp plans to respond quickly to IBM's announcement of 4GB drives for the 9337 with its own 4GB announcement. The company also hopes to establish the 9638 disk array as a platform that customers can upgrade to new drive and controller technologies as they emerge.

Tips for the Negotiating Table

As this review of vendor strategies makes clear, midrange DASD vendors live in a world of tight competition. What's more, the competition is getting even tighter. IBM now realizes it has lost market share because its sales representatives were less aggressive, less educated about DASD and less willing to negotiate prices and terms than its competitors. As a result, it is changing its old habits in order to maintain market share or even win back the share it lost in the early 1990s. The plug-compatible vendors are responding to IBM's change aggressively.

You can take advantage of the buyers' market this situation creates if you take the following steps. First, assemble an acquisition team that has the authority to establish your storage priorities and make the purchase. The team should write up a list of the qualities and capabilities you need and rank them by order of importance. For instance, is performance more or less important for you than high data availability? Furthermore, what levels of performance and data availability do you need? Getting answers to these and other questions may require some research, but the time spent in this activity will be well worth it.

Second, collect data on products that meet your priorities and on the vendors who build them. A good place to start your research is the buyers' guide chart within this article. You should also learn as much as possible about your prospective vendors and their competitive strategies. Talk to as many of the vendors' customers as possible to learn about the tactics the sales representatives use, the terms and conditions they offer and the concessions they make. If possible, find out what the true costs of production are. According to Reliability Research of Needham, Massachusetts, the average 6.8GB array system currently costs around $1.68 per MB to develop, manufacture, market and support.

With this data in hand, you can take the third step of collecting and evaluating bids. While you are doing this, avoid revealing certain "vital statistics" to inquiring vendors: your buying criteria, your budget and the competitive products you are evaluating. On the "do" side, be sure to have at least two bidders. This lets you take advantage of the fierce rivalry that is typical of the storage market. In addition, insist that vendors itemize prices for everything rather than bundle products and services together.

Look for opportunities to press for concessions on prices, terms and conditions; these opportunities frequently come at month-end and especially at the close of the quarter. Finally, be sure to get everything in writing: a vendor's verbal promise means nothing. By taking these steps, you can leverage the competitive environment existing among DASD vendors, maximize your chances of getting the optimal storage subsystem for you and save thousands of dollars in the process.

Lee Kroon is the industry analyst at Midrange Computing.

GLOSSARY

Aereal Density: The amount of data a disk can contain in a given amount of space. Aereal densities are usually measured in megabits per square inch.

Buffer: A dedicated memory device that collects data being read from or written to a peripheral. Buffers minimize the amount of time a CPU must wait during an input/output operation, thus improving system performance. Most AS/400 disk controllers contain read or write buffers.

Cache: A buffer that uses intelligence in microcode to improve effectiveness. Read caches anticipate the data the system will need; write caches determine optimal times to perform write operations. Most AS/400 disk controllers contain write caches, and many non-IBM controllers contain read caches.

Checksum: A software-based, data-protection scheme that groups disks into sets of two to eight disks, then spreads parity information across the set. In case of disk failure, the system uses the checksum algorithm to recreate the data from the failed disk.

Disk Mirroring: The duplication of the contents of one or more disks on a second group of disks. The AS/400 has built-in software that mirrors disk devices as well as controllers, IOPs and system buses. In addition, some disk arrays can perform their own mirroring without AS/400 assistance. This is known as subsystem mirroring.

Dynamic Spare Disks (also called Hot-Spare Disks): A data-protection and recovery technique in which one drive is reserved as a spare within an array of drives. If one of the drives in the array shows signs of an impending failure, the data on the failing drive is written to the spare, which then becomes active. Hot spares are only as good as the array's ability to predict a failure.

Mean Times Between Failure (MTBF): The average amount of time a component operates before a failure occurs.

Redundant Arrays of Inexpensive Disks (RAID): A method of maintaining high data availability by building data-protection techniques into an array of disks. Redundant Components: A method of protecting an array from failing by adding reserve parts to the unit. Some common redundant components are disk drives (called dynamic spares), power supplies and cooling fans.

Seek Time: The total time required for a disk device to read or write data. While most vendors provide the average seek time, some cite minimum seek times, so make sure you know what you are being quoted.

A WORD ABOUT 9404 DASD

If you are the proud owner of a 9404 AS/400, you may be wondering if anyone besides IBM has a reliable storage solution to offer you. The good news is that there are alternatives. IPL Systems, for instance, offers the 7100 series. The series includes both single-disk and dual-disk models that offer capacities of 320MB, 400MB and 1GB. Within a month or two, the company will also market 2GB models in single- and dual-disk configurations.

EMC Corporation is also planning a 9404 disk series. Its models will range from 400MB to 4GB and will be compatible with 9404s from the oldest B-series model to the newest F-series system. Expect the company to announce the new product line in April.

VENDOR INFORMATION

Decision Data A Division of IIS 400 Horsham Rd., Suite D Horsham, PA 18966 800-879-5255 215-957-9500 fax: 215-957-0219

EMC Corporation 42 South St. Hopkinton, MA 01748 508-435-1000 fax: 508-435-3079

IBM Corporation Contact your local representative

IPL Systems, Inc. 124 Acton St. Maynard, MA 01754 508-461-1000 fax: 508-461-1316

Memorex Telex Corp. 545 E. John Carpenter Fwy. Irving, TX 75062 214-444-3500 fax: 214-444-3577

XL/Datacomp, Inc. 801 Warrenville Rd. Lisle, IL 60532 800-323-3289/ext. 2443 fax: 708-434-1254

Buyer's Guide: 9406 Direct-Access Storage Devices

Figure 1 The Five Segments of the DASD Market

 o Unprotected, high-capacity: These products use the latest high-density drives to pack the most data in the smallest space. Some of them also serve as high- availability models because they offer disk mirroring at a reasonable price. IBM's 9337-040 and EMC's HX3C are typical examples. o Unprotected, high-performance: These arrays use low-density drives with the same number of read/write heads found in the high-density units. This puts less data under each head and increases throughput rates. Like their high-capacity cousins, many models can perform disk mirroring. IBM's 9337-015 and Decision Data's 9036 fall into this category. o High-availability, high-capacity: This group offers high-density drives along with built-in disk-mirroring and/or RAID5 abilities. Some models can switch between unprotected and high-availability modes. IBM's 9337-240 and IPL's 7037- 40 are good examples. o High-availability, high-performance: This group also offers mirroring or RAID5, but uses low- or medium-density drives for greater performance. IBM's 9337-215 and XL/Datacomp's 9638-120 typify this category. o Fault-tolerant: Besides offering RAID5, these storage devices include multiple redundant components to guarantee high levels of continuous operation. XL/Datacomp's Alpine 9600 array and the 3937 series from Memorex Telex are typical examples.