The very first "pre-CLARiiON" version of FLARE (CLARiiON's microcode) supported two RAID levels: RAID-1 and RAID-5. Due to the "RAID-5 write penalty" it was clear that we needed to provide an alternative protection scheme that could handle heavy write workloads. RAID-1 was our answer.
We characterized the performance of our RAID-5 solution and instructed customers that if their applications were performing highly-transactional, multi-threaded disk operations at about a 70-30% read-to-write ratio, then RAID-5 would perform well. For a higher percentage of writes, use mirroring. We had I/O per second (IOPS) characterizations that helped customers make the choice.
Well there was one application that slipped through the cracks, and our RAID-5 performance was so bad that the executives at DG considered putting the FLARE team on the chopping block again. How bad was it?
How about 12 I/Os per second?