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Sizing for an A-Class migration

Migration planning includes trying to calculate how much Unix box you'll need to replace that HP 3000 system. While customers have given the newer generation of 3000s good marks compared to the 9x9 and 9x8 servers, one report we saw recently confirms what HP claims: Moving out of the hampered MPE/iX environment which HP slapped onto the A-Class servers will give you some performance room. It seems that those A-Class 3000 systems, just like nearly all of the N-Class servers, aren't running as fast as they possibly can.

The report was just the latest entry we've heard about how HP's held back the 3000 line compared to its Unix counterparts. HP has actually told 3000 customers this is a benefit — at least that's the way it's presented to a room of customers who are asking questions about migration. This time Duane Percox of QSS was answering the following question from a migrating user:

We currently have an HP 3000 A-500 140 2-way, running a client server application using an IMAGE database and ODBCLink as the middleware. Would a RP3440 2x1GHz  PA8900 CPU with 4 GB memory, compare in speed and performance? We are going to convert the IMAGE database to Oracle. Just trying to get an idea.

The answer began with a warning: You might not have as much HP 3000 power to replace as you think you do.

Percox answered with a set of notes, based on his company's tests of COBOL applications on HP's Unix systems (details at saying:

• Your A500-140 is not running at 140MHz as advertised by HP. Due to CPU throttling, that may or not be as good as could be. You are actually looking at closer to 72MHz for that A-Class

• Throttled A-Class boxes also exhibit interesting IO timing issues as demonstrated by some very astute folks who would know, given their intimate knowledge of everything MPE. Here again you might not have as big a box as you think you have.

• I haven’t managed a production Oracle system, but from what I have read you probably want more memory than 4GB for that system if it is going to be an app and database server. I would start at 8GB, and consider even more depending on the number of connects.

• Make sure you are getting a 2-way server. I would never recommend running a relational database server with less than a 2-way. And you might even need a 4-way depending on the number of connects.

• Make sure you connect that new server to your network with gigabit LAN.

• You didn’t mention disk subsystems, which have a big impact on database performance. And no mention of the number of database connects, which also has an impact.

•  I find that moving from TurboIMAGE to relational is about a 10-12x CPU hit for the parts of the app that are managing the database. Since your app also spends time doing other things, you don’t necessarily have to have 10-12x the CPU, but it might be a reasonable starting point.

• You are wise to get a 3440 system so you can put two more CPUs into it if needed. Also, the more CPUs the more memory (a vicious cycle). I assume you are starting with 2x1GHz in that 3440. Once again I will point out: minimum config is a 2-way.

• The MPE TCP/IP stack is performance challenged, so you will see networking improvements when migrating to HP-UX.

• TurboIMAGE/ODBCLink isn’t a performance screamer, so you might be in for some pleasant surprises in the positive direction.