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

MOPSOMER@raychem.com wrote: > > We plan to move our Informix databases to an EMC2 3700 box in the near [SNIP] > > 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 ? I personally LOVE RAID10 (ie stripped mirrored pairs) building stripe sets of from 16 - 32 mirrored pairs (16 drives is what the TPC benchmark group uses for the tests, even if you doubt me you gotta believe that the Informix benchmark group is trying to max performance). For Informix drives make sure that you reduce the default stripe block size. Most striping firmware wants to use 64K or 128K for a block size which works VERY well for filesystems with larger files but is death for an Informix database that is not doing a huge number of sequential scans. The optimal stripe size for Informix seems to be 8K or 16K (Informix BIGREADs are 16K and normal reads are 2K all writes are 2K but the page cleaners batch writes so that the controllers and drivers should compress multiple writes into a single larger one). The only gotcha of ROUND ROBIN striping is that you will get better performance if you detach all indexes either into a single dbspace or fragment each index by an expression based on its key value. Art S. Kagel