Over the next several months, thousands of iSeries customers will put their server upgrade options under the microscope to determine how they should add capacity to their systems. In previous articles, we have examined upgrade options for most iSeries 8xx models. However, there are three models that we have not covered: the iSeries 825, 870, and 890. In this article, I'll offer the users of these models some guidance that will be useful not only for them, but for all iSeries owners.

In a break with tradition, let's start this article at the high end of the iSeries and work our way backward. Those of you who own an iSeries Model 870 or 890 have been patiently waiting for me to provide the kinds of analyses that I've offered to owners of smaller servers. Guess what: I have some good news and some bad news for you. The bad news is that you will have to wait a little longer. The good news is that you will get a special reward for your patience.

I know that many of you have been expecting IBM to announce a high-end eServer i5 model that has more than 16 processors. I also know that many of you would consider such a server as an upgrade option. I can assure you that you will get to consider that option very soon, although my agreements with my IBM sources prevent me from saying when. However, as soon as Big Blue announces this new model, I will offer you an article that examines it as an upgrade option along with the current Model 570. If you want to know more about the upcoming announcement, I would advise you to contact your IBM representative, who may be at liberty to tell you more.

About the Model 825: Solving an Upgrade Riddle

If you own an iSeries 825--or for that matter, another iSeries model in the same performance class--there is something that you should know about upgrades to the eServer i5. One of IBM's rules for upgrading within the eServer i5 family might make it more challenging for you to pick the right upgrade option than for owners of entry-level or high-end servers. The rule to which I am referring is the one that limits eServer i5 customers to upgrades within each model number in the new POWER5 processor family. By contrast, several iSeries 8xx models, including the Model 825, can be upgraded within their model number or to a faster model, such as the 870.

Some industry observers claim that this makes the eServer i5 family significantly less flexible and "upgradeable" than the current iSeries 8xx. As the following table shows, this claim has little ground to stand on except in the middle of the eServer i5 performance range. The table shows the effective upgrade performance range for each iSeries and eServer i5 model. The range is determined by dividing the highest CPW rating that any given server can achieve through upgrades by the lowest CPW rating at which a customer could put it in service.

As the table illustrates, customers that acquire a Model 520 or 570 can take advantage of expansion options that give them more performance headroom than an iSeries 8xx with comparable performance. For instance, a customer that upgrades to a Model 520-0902 (rated at 1,000 CPW) can use upgrades and processor activations to grow their capacity by six times. By contrast, an owner of a comparable iSeries 810 can only expand the server's capacity by 3.6 times. As for Model 570 owners, they enjoy an effective growth range that is greater than that of any iSeries 8xx model.

The Model 550, however, is a different story. While this model provides an effective growth range of 3.6 times, the Model 825--which is in the same performance class--offers a growth range of 10.4 times. Of course, IBM can rightly argue that if customers need more CPW headroom than the Model 550 provides, they can always purchase or upgrade to a Model 570 and get that extra headroom. That's true, but the Model 570 costs significantly more than a Model 550 with comparable performance. Besides costing more on a per-CPW basis than the Model 550, the Model 570 is more expensive to maintain and is in a higher software price tier.

In IBM's defense, let me say that the company is not permanently boxing Model 550 owners into a limited growth range. When Big Blue announces the next generation of eServer i5 models--an event that will probably take place in roughly two years--it will provide upgrade paths from the Model 550 and all other 5xx servers to the new systems. However, what happens if you purchase or upgrade to the Model 550 and exceed its capacity before the next server generation ships? This could be an issue for those of you who own a Model 825 or another iSeries with comparable performance, as the Model 550 could be an attractive upgrade path for many of you. Before you take that path, however, you should carefully consider your capacity needs and discuss your options with an IBM representative.

While the upgrade paths to the eServer i5 still contain some unexpected twists and turns, the overall POWER5 roadmap has become much clearer over the course of the summer. As we enter the fall season, look for IBM to finish the task of rolling out those systems and refining the terms and conditions for acquiring them. That should give customers plenty of time to make fully informed purchase decisions about the new servers with whatever budget authority they have for the current calendar year.

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..