IBM Explains New p5 Boards, Offers Upgrade Protection to Power6
Published: May 11, 2006
by Timothy Prickett Morgan
In last week's issue, I told you all about the new Power5 Turbo processor boards that IBM announced for the high-end System p, formerly the pSeries, servers--specifically, for the p5 595. I was somewhat mystified by the announcement, since the new processor book--what other vendors call cell boards--had the same technical specs as the one it replaced. This week, Big Blue cleared up the mystery and also offered some insight into its upgrade strategy for big p5 machines to make them upgradeable to the future Power6 servers.
To recap: The new Power5 Turbo book, feature 8969, has exactly the same technical features as the Turbo book it replaces, which is feature 7813. They both are based on the 1.9 GHz Power5 processor, which you can see from the feeds and speeds. Last week, I said the lack of explanation was very fishy, and mostly because IBM did not offer any explanation. I added that IBM was offering a feature upgrade to allow customers to move from the old Turbo book to the new one, and that the customer announcement letter IBM put out did not say customers were required to move to the new board, so it may not be anything ominous. As it turns out, the new Turbo board is indeed not ominous.
In fact, the new feature 8969, board is based on a new multichip module (MCM) package that includes support for a larger virtual memory page sizes, explains Jeff Howard, director of System p marketing. With the Power5+ machines that IBM started rolling out last fall and continued to roll out this spring, the AIX kernel can be tweaked to support 64 KB or 16 GB memory page sizes rather than the default 4 KB size. These changes in memory paging are handled by AIX, and IBM's technical specs on it (which you can read in this redbook put out by Big Blue) suggest that 64 KB page frames can significantly improve performance. This redbook further suggests that so called "huge page" support, which is for 16 GB pages, is intended only in "very high performance environments." Basically, if our applications are swapping huge chunks of data in and out of memory, doing it with very big handfuls--say, 16 GB instead of 64 KB--reduces processing associated with allocating memory, which means the application will speed up.
Customers have to configure AIX to use 16 GB memory pages using the Hardware Management Console. Both 64 KB and 16 GB page support require AIX 5L V5.3 with the 5300-04 technology level (what we might call a sub-release) and you have to be using the 64-bit AIX kernel.
In any event, Howard says that customers who buy these boards today will be able to run a firmware patch on their p5 595s and activate 16 GB memory page support some time in the second half of 2006. It is my guess that this firmware patch will come out concurrent with IBM's expected delivery of transportable partitions on the Power-based server line. I am also willing to bet that for many customers, this huge page memory support is more important than clock cycles for many of their workloads, which would be why IBM would go to the trouble of backcasting the technology into its 16-core, 1.9 GHz Power5 books for the p5 595s.
Power6 Upgrades Planned
The most important features of a large enterprise server--a mainframe or a big Unix or OS/400 box--are not its processor, its memory controller and cards, or its wickedly fast I/O subsystem--at least not as far as accountants and the IT managers who have to tangle with them are concerned. No, sometimes, the most important part of such a behemoth is the serial number that is riveted to the back of the machine. Why? That silly metal plate defines an item that can be depreciated as a single unit, and the law, which accountants are supposed to follow, determines the depreciation schedule for that machine.
So who cares, right? Well, an IT manager who is considering buying a System p5 590 or 595 server today, which could easily cost millions of dollars when configured, cares a great deal. If IBM doesn't offer upgrade paths from the current machines to the future Power6 machines, then the IT manager will have to tell his boss, the CEO, and the CEO's henchman, the CFO, that they need to do a box swap when they move to Power6 technology. If the old box goes out the door--the one with that silly metal plate with a serial number on it--then that box has to be immediately written off, and then the whole value of the incoming System p6 machine would have to be put on the books. This messes up the bottom line, as you can imagine, which is why big enterprises with big iron like to upgrade their machines rather than do push-pull replacements.
So IBM has issued a statement of direction that explains the company will indeed be offering an upgrade path from the current Power5-based p5 590 and 595 servers into the next-generation Power6 machines, which are due in 2007. IBM did not say anything about upgrade protection for the p5 570 machines, which already have Power5+ processors in them running at 2.2 GHz. But Howard explained that IBM generally does not offer upgrades for entry and most midrange machines, since these are fairly inexpensive machines and the process of creating the upgrade paths and testing them all is a pain in the neck. "Generally, customers replace entry Unix boxes with new ones and then repurpose or get rid of the old ones," he says, adding that IBM used to offer such upgrades in its entry and midrange RS/6000 and pSeries lines and the uptake by customers was never that great. IBM does, however, offer upgrades, even with Power5 and Power5+ machines, in the very similar iSeries and System i product line, where customers tend to upgrade rather than do box swaps. The difference is cultural, not technical.
By the way, apparently a server vendor can't just call something an upgrade just because it wants to preserve a serial number to avoid having its customers write off their investments in one fell swoop. There are rules about how memory subsystems, I/O subsystems, and other core components have to move forward. Howard explained that IBM has its own internal guidelines as well for determining when it can and when it cannot call a change in server technology an upgrade.
In any event, according to Howard, customers with Power5-based p5 590 and 595 machines will be able to upgrade directly to Power6 machines, and those with Power5+ chips in their p5 590 and 595 servers will also be able to jump to Power6. Customers will not have to move from Power5 to Power5+ and then to Power6.
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