Some say it's faster storage, and others claim it's extra CPUs. But the one item that any 3000 customer can add to their systems to improve performance is almost always memory. Unlike processors, upgraded systems or other things HP simply doesn't make anymore for the 3000, memory has always been available from third parties. How much to add depends on who you ask.
HP has weighed in on memory needs for MPE/iX on its Jazz Web site. In a white paper written a couple of years ago about investments in disc storage, HP's Walt McCullough said that the 3000 is designed to go to disk only when what it needs is not in memory. Therefore, he says
The greater the amount of memory for the HP e3000, the more efficient it will run (to a point). MPE uses available (server) memory as a cache to store user process information and also keeps a virtual copy of the file.
But add to what point? Ask Bill Lancaster, CTO of Lund Performance Solutions, and he'll give an answer that has more to do with a CFO than a CTO. "The best axiom about memory on MPE is to buy all you can. Very, very rarely is there such a thing as too much memory."
Lancaster explains that MPE's memory utilization
is best viewed from the perspective of how effective it is in acting as a cache. The two top metrics in evaluating this are Read Hit Percentage (the percentage of all read IO’s satisfied in RAM) and CPU Busy on Memory Management. You want a Read Hit Percentage in excess of 95 percent and CPU Busy on Memory Management less than 4-5 percent.
Users report that memory is "so cheap now it's really a no-brainer" to add it to HP 3000s. The "add as much as you can buy" rule of thumb might trump another guideline, one recounted by Dave Waroff of the San Juan School District: 64Mb/CPU + 16Mb (for the 3000's Transaction Manager) + 8Mb/batch job + 4Mb/session.
If you're unable to buy all the memory that you can fit into your 3000, and some more strategic measurement will help, then Lancaster's firm offers a good multi-platform solution to measure anything on a Unix, Windows, Linux or MPE/iX server. Meta-View Performance Manager includes Lund's Performance Gallery Gold suite. It's a product you can use to justify an optimal memory configuration and improve performance. Not bad for an add-on that is "so cheap now it's really a no-brainer."