isham research
The z890 uses the latest z990 technology to deliver unparalleled flexibility with 28 different performance points. From 27 to 1364 MIPS, it covers a performance range of 1:50 - the same ratio covered by the entire IBM System/360 range announced exactly four decades to the day before it.
Using z990 technology has many benefits for IBM. Firstly, the development costs have been amortised. Secondly, lower performance requirements permit the use of processor chips that are perfectly functional but just don't pass the stringent tests required to meet z990 cycle times. The z890 uses "reject" chips exclusively - these are chips that have one defective and one good processor core. Thirdly, technology such as microcode, the service processor, I/O frames, etc., is available off the shelf.
The advantages for IBM's customers are just as pronounced. The technology is proven and ready for "prime time". Connectivity is much the same as the z990 - the same peripherals are supported in the same way. Although the z890 Capacity Setting 110 will be IBM's smallest zSeries system, there is no provision for integrated DASD - a free-standing DASD subsystem is required.
The novelty is that IBM now offers all performance levels (seven) in all configurations (four) leading to a matrix of 28 different submodels. The z890 can - between around 90 and 330 MIPS - provide much the same performance in a choice of one-way, two-way, three-way or even four-way configurations. This addresses the concerns of many who would otherwise face a reduction in the number of processors when upgrading to a more modern system. All of IBM's current mainframe systems are fully populated - users can already switch extra processors on pretty much at will. Turning two on at half power rather than one at full power suits some software much better - four at a quarter power even more so. Once it's done it's so obviously a better way to tackle the problem that it's amazing it wasn't done before.
At the very low end, the system is placed right into the n-way performance space that was the exclusive domain of the emulation providers. At ca. 65MHz per MIPS, emulation easily provides 26 MIPS on a 1.8GHz Intel processor. Using a 4-way xSeries server and reserving one processor for the host UNIX or Linux yields a 3-way with up to 65 MIPS. IBM now has a pure hardware offering in this space, with a significant connectivity advantage - though emulation retains many functional advantages in the areas of operating system support, integrated DASD, pseudo-tape handling, etc.
There are other, more bizarre, novelties. For the first time it's possible to "upgrade" a system to one with fewer MIPS - and pay more for some software!
Having only five PU chips means flexibility is restricted - four at most may be used as instruction processors, coupling facilities, zAAPs or IFLs. Since the z990's relatively expensive cooling system has been omitted, the processor cycle time must be increased; reducing the UP power from 450 to ca. 365 MIPS. There isn't a great deal of point in overlapping the z990 itself by very much, either - although the z890's ceiling of 1364 MIPS will provide most users with adequate capacity to cover application growth during its operational life.
Software charging will be an interesting issue. There is only one model - the 2086-A04. The performance of the system is determined by a Capacity Setting. This is a three-digit number, although only the first two digits are significant. The first of these indicates the number of processors - 1 to 4 - and the second indicates the degrade level from a high of 7 to a low of 1. The smallest system - the 110 - will use zELC pricing; the others will use EWLC.
This matrix is interesting, because there are several performance points in a diagonal band from one corner to another that can be met by several variants. Take, for instance, 90 MIPS:
Much the same is true up to 320 MIPS:
Some of these systems are likely to prove more popular than others. An upgrade from a 6x20 to a 6x30 brings 47% more performance, but an upgrade from a 6x30 to a 6x40 only 20%. There's a further reason - because of the rule that the target machine for an On/Off Capacity Upgrade on Demand cannot exceed twice the power of the source machine, the 6230, 6330, 6250 and 6350 offer greater CoD flexibility with three possible target performance points, against two for most of the others.
But, once again, the hoary old issue of software pricing rears its ugly, wart-covered head. A lot of software is priced per engine - z/VM, WebSphere Application Server ES, Linux distros - and this produces some extremely bizarre effects. Assuming the Ts&Cs require all engines to be licensed at the same price, a 328 MIPS 430 would cost four times as much as a 366 MIPS 170. For this reason, z/VM will have a lower entry price on the z890 and will be progressively cheaper for each engine licensed.
Broadly speaking, the performance matrix has three significant areas:
With the absence of plug-compatible competition, the z890 has no competitors at the medium and high ends of its range. Older hardware is increasingly unable to run operating systems and middleware that require the newer architectural level sets (ALSes). With 28 performance levels and configuration flexibility, the z890 is perfect for those who want to start server consolidation with a system capable of great expansion but without having to make major up-front commitments. Since the progress of server consolidation is often limited by political considerations and may sometimes stall, this is a significant advantage.
The z890 could be with us for a long time. There are several very viable options for a mid-life kicker, including replacing the processor chips with twin-core versions to build a 2086-A08. Although the upper right quadrant of the performance matrix would then clearly overlap the z990, the z890 is a much cheaper machine to produce and has more than sufficient I/O connectivity to occupy the space.