For years, IBM has made at least one significant System i announcement during January or February. In keeping with that tradition, the company will unveil new storage subsystems for the System i tomorrow. While this year's announcement may not be as splashy as some, it will matter a great deal to companies that are demanding faster and more flexible storage for their mission-critical applications.

In response to those demands, IBM will announce a disk controller that delivers about 30% greater I/O throughput than the #2780/5580 controller does. Besides beating the former throughput champion, the new controller supports RAID-6 as well as RAID-5 storage protection. While RAID-5 enables a disk array to continue running if one disk in the array fails, RAID-6 allows two disks in the array to fail. In addition, the new disk controller does not require an I/O processor (IOP) when used in a Model 5xx system running i5/OS V5R4. Depending on the configuration, this could save users money as well as precious PCI slots in their systems.

The new disk controller gets its muscle from the POWER-PC processor at its heart and the enormous 1.5GB read cache and 1.6GB write cache that it packs. These caches enable the controller to improve the performance of the increasingly larger drives that many customers are deploying. According to IBM performance experts, the new controller should definitely be considered by any System i shop that is running 70GB or larger drives.

While the new controller is a cut above its peers, it costs no more than they do. As the following table shows, the device costs $6,200 without an auxiliary write cache and $6,995 with the cache. These prices are identical to those for the #2780 controller (which has no auxiliary cache) and #5580 controller (the #2780 equipped with an auxiliary cache).

While the new controller has definite advantages over prior designs, there are some things you should know about the device before you buy one. First of all, it requires i5/OS V5R3 or higher. While it can run in a #5094/5294 expansion cabinet, it is not compatible with the #5095/0595 or #5074/5709 cabinets. It also will not run in the system cabinets of most iSeries 8xx models, with the exception of the Model 825. In addition, you must pair up the controller with a new 1.5GB auxiliary write cache I/O adapter if you want to use the controller in a RAID-5/6 array. While IBM strongly recommends that owners of #2757 and #2780 controllers purchase auxiliary write caches for their RAID arrays, the new controller is the first one to require such a cache.

That said, the new controller is a clear step ahead of what companies are currently packing in their servers. If your performance reports indicate that your iSeries or System i is I/O-constrained, you should seriously consider the device. By the way, if you exchange your #2757 or #2780 controller for the new controller, you can take $1,000 to $2,000 off the purchase price.

A New Way to Package System i Storage

For over a decade, little has changed about the way that IBM packages disk storage on its midrange servers. That all changes tomorrow when the computer giant unveils the TotalStorage EXP24 Disk Enclosure. The new rack-mounted enclosure packs up to 24 disk drives into a 4U-high space. That equates to 840GB of storage when using 35GB disks and over 1.5TB when using 70GB drives.

The EXP24 achieves its formidable density through its unique design. Unlike traditional expansion cabinets, the EXP24 has no PCI slots for disk controllers or other adapter cards. It only has disk slots that are configured in one to four "packs" of six slots each. These "six packs" connect to disk controllers via SCSI cables that can be up to 20 meters long. The disk controllers reside in the System i central electronics cabinet or a conventional expansion cabinet, such as the #5094/5294 or #5790.

Since the EXP24 lacks PCI slots, it can pack more disk storage into a smaller space. Indeed, a full rack of EXP24 enclosures can contain more than twice the disk storage of a #5294 expansion cabinet in the same amount of floor space. That includes the space required for the disk controllers, which can reside in a rack-mounted #5790 expansion cabinet. The EXP24 also gives customers increased flexibility over where they locate their storage, since they can place disk drives up to 20 meters away from their controllers. In many cases, this can allow storage subsystems to reside on a different floor than their system cabinets.

Besides its density and flexibility advantages, an EXP24-based storage array can often cost less per gigabyte than a conventional array. While this is partly due to the pricing of the EXP24 enclosure itself, much of the savings is derived from a new disk controller that IBM is also announcing for drives housed in the EXP24. The new controller, which sports the same large read and write caches as the high-performance controller discussed earlier, can support up to 36 drives. Because the controller supports far more drives than other controllers do, it can significantly reduce the overall cost per gigabyte of a storage subsystem. As a rule of thumb, IBM has found that an EXP24 enclosure with more than 12 drives that uses the new controller will usually cost less than an equivalent array running in a conventional expansion cabinet.

If the TotalStorage EXP24 Disk Enclosure sounds like an attractive proposition for your company, there are a few things you should know about the device. It requires an iSeries Model 800/810/825/870/890 or System i running i5/OS V5R3 or higher. Any EXP24 disks that are connected to an i5/OS partition must be 15K RPM drives. When connected to Linux or AIX 5L partitions (yes, the EXP24 supports Linux and AIX 5L partitions too), the EXP24 can use 10K or 15K RPM drives. By the way, the EXP24 supports RAID-6 arrays when connected to the new high-capacity disk controller.

More to Keep in Mind

While the EXP24 and the high-performance disk controller will be the stars of tomorrow's product parade, other announcements will play supporting roles. Among them will be the #5096/5296 I/O Expansion Tower. The #5096 is, in essence, a #5094 Expansion Tower with all of the disk slots removed, leaving only 14 PCI slots. The #5296 is a #5294 tower with no disk slots, leaving 28 PCI slots. The two diskless cabinets will appeal to customers who need more PCI slots, but not disk slots. With its 14 PCI slots, the #5096 can act as a substitute for the #0588/5088 PCI Expansion Unit that IBM withdrew from marketing last year.

Speaking of withdrawals, IBM will also announce the withdrawal from marketing of roughly 90 older feature codes tomorrow. Products destined for the chopping block include the VXA-2 and VXA-320 tape drives, around 50 USB keyboards that have been replaced by other boards, and a hodgepodge of other minor features.

Finally, IBM will use tomorrow's announcement to provide customers with planning information about the I/O devices that it will not support beyond today's System i Model 5xx family. Today's models will be the last to support the following devices:

• The #5074/5079 I/O towers
• Optical HSL cables
• 8GB and 17GB drives running at 10K RPM
• Several older PCI cards, including the #2763, #2782, #4748, and #4778 disk controllers
• Several older tape drives, including the 9348, 3570, 3575, and all QIC tape drives with capacities of 25GB or less. New systems will also lack support for VXA tape drives as well as 3490 and 358x tape drives when attached via the #2749 controller.

While IBM is cleaning house on older I/O devices, its announcements point the way to a future in which System i storage is faster, cheaper, more flexible, and increasingly rack-mounted. This does not mean that IBM will abolish traditional expansion units and towers; indeed, sources inside the company say they have new expansion towers on the drawing boards. However, tomorrow's announcements indicate that the System i will take increasing advantage of the density improvements that rack-mounted form factors have to offer. That is a trend that space-strapped customers will definitely applaud.

Lee Kroon is a Senior Industry Analyst for Andrews Consulting Group, a firm that helps mid-sized companies manage business transformation through technology. You can reach him at This email address is being protected from spambots. You need JavaScript enabled to view it..