Re: Informix 7.24 with SAP R/3 : EMC2 : striping / fragmentation

Based on the large SAP/Informix/EMC sites I've seen, even Sun's largest servers will run out of CPU cycles before exceeding the 'total bandwidth' of an EMC 3700 or SSA rack. Large tables and indexes (>20GB) whether fragmented, striped or not, must be spread over > 10 2GB devices (20 physical disks) and therefore are rarely a problem. The trouble makers are the 0.5-2GB tables and indexes that are 'hot'. They create disk bottlenecks because they are too big to be cached and too small to be spread over concatenated chunks in a dbspace. In this case, either fragmentation or striping can be used to spread them over five 2Gb logicals (10 physicals) which is usually enough. Finally, the EMC Symmetrix DMSP (dynamic mirror service policy) will help in this case by both increasing I/O concurrency (employing both mirrors) and by reducing disk service times by servicing the 'outside' hypervolumes from one mirror and the 'inside' hypervolumes from the other mirror. > QUESTION : > ---------- > Do any of you have a large OLTP environment with EMC2 and Informix ? > If so, did you use disk striping or did you fragment database tables ? > Any opions about striping and round-robin fragmentation with EMC2 HW ? > > Thanks in advance, > > Mario Opsomer > Informix DBA - SAP BC Support