Alexander Sabourenkov wrote:

Hm... two points here. I, somehow, do not really believe that software raid (gmirror for example) is as reliable as hardware. I, deeply inside, believe that i might screw things very badly under some heavy load and bad timing conditions. Can't explain it. it is religious i guess, but i can be very wrong about this.

However, two perfomance point: Under gmirror OS must issue two commands to write to disks and some commands to check/set mark that mirrored data is intact. Under hardware RAID OS issue sonly one command to write and no checking command, since raid controller handles this async.

So, software OS raid must be slower than controller based raid anyway.

Am i right here? Any benchmark data on this?

As for reliability of gmirror. I just need to know how it works to see for myself that if power turned off in some racing condition gmirror will know
that disk are out of sync. If it is done than gmirror must check sync of disks every
read, and that mean two command for reading too, which must slow down things. Is it true?