1) Let's say I have an array of twelve disc drives in a RAID-1 formation. That's effectively six drives presented for use. What's the maximum read rate I should be able to get out of that array? Let's say each drive maxes out at 40 MB/sec. Does that mean I should be able to read (up to) 240 MB/sec from that array? Or will I only ever be able to get a maximum of 40 MB/sec read rate, regardless of how many drives in the array?
2) If the answer to the first question is 240 MB/sec and yet I'm getting only 40 MB/sec out of that array, what could be the problem? Where do I start diagnosing this?
3) As you've probably guessed by now, this is an actual problem I'm having right now. Up until recently I was able to read up to 200 MB/sec out of this array, but then, after a simple re-boot of the server, I'm getting just 35 MB/sec. What could possibly have caused this? I'm baffled. There doesn't appear to be anything physically wrong with the hardware. All appears to be working normally. What am I missing? Some "parallelize/striping" parameter that has reset itself? A dead battery in the RAID controller? The RAID array in question is directly attached within a PowerEdge server, which in turn is used to host a SQL Server instance. The RAID array stores the files for just one database.
Any and all help gratefully received!