Sounds about right to me. Wasn't intentional.
I watched part of this on Courttv the other day. It seems that there are lax inspectors, poor bar management, etc. that may have a hand in the blame as well. Even the father of one of the deceased said that they needed to go after some of the other folks, not just this guy.
I'm sure most of the families are angry at the sentence, but if (and I didn't hear all the testimony) the defendant was given the go ahead by bar management, and he had done this sort of pyrotechnics before in similar clubs, I don't know that a long sentence is the right punishment. I'll be honest and say I don't know if I'd feel the same way if my child or spouse had died in the fire.
Hence the charge of involuntary manslaughter rather than voluntary manslaughter.