> isolated requests, obviously in scale the RAID should perform better... I > have not started testing concurrent reads in scale as the single reads are > too slow to begin with. I am getting 20-30ms response time off of internal
Concurrent reads is what you need to do in order to see the benefit of a RAID controller with many constituent drives under it. > drives and 50-70 ms response time through the raid volumes (as reported in > cfstats). The system is totally idle and all data has been cleanly That said, a RAID controller imposing several tens of extra milliseconds of latency sounds strange; something else or fishy has to be going on. But don't expect sequential reads of non-cached small random-access data to be faster with a RAID controller. The benefit of RAID will tend to be overall throughput when doing concurrent reads, fast fsync() (low latency on durable writes) and the ability to eat bursts of write activity in battery backed cache. -- / Peter Schuller aka scode
