Machine Configuration

Hi everybody. We have a version 7.20 of Informix OnLine Dynamic Server on a DEC 2100 with 3 CPUs, 1 GB of RAM and 60 GB of Storage Array. Everything is OK, but we want to find the best configuration for the disk array. We have 2 disks array of 30 GB each, on 2 different controlers, each one with 4 channels. Each array has 6 HZ40 from DIGITAL, that support bolth raid level 3 and 5. Probally, we will have much more "READS" than "WRITES". We know that there is a big difference from raid level 3 and 5 when reading information from a database, and in bolth cases the chunk size parameter is very important. Does anybody have any experience on it. Witch configuration can be experimented with these disks and controllers. We are using LSM (Logical Storage Manager - from DIGITAL) to create the logical devices (disks). Of couser, this will slow down the performance, but it will improve the flexibility. Well, has anybody configured a system like this. Where and how can we find some help. Where and how can we get a program and dates for a test of performance. Thanks in advance. OBS: Sorry for my English.