iMac screwing with hard drives, formatted one of them

I got a refurb 27" 2013 iMac a few months ago. I go thru tons of hard drives for my job, so for years I've used 'internal' 3.5 hard drives and just stick them on a mount thru firewire. I've done this with at least three different apple computers and never have had an issue with a hard drive or connections.

So I set up the same system on the new iMac, except I don't have firewire.

The thunderbolt dock, which is 1 of 2 on the market, constantly disconnects. So I switched to my old firewires and got a converter to go thunderbolt. Now 3 out of every 5 HD's I buy don't get recognized by the iMac at all so I can't format them. Yet I can see them on my old MBP? And a few have fail. I switched brands and then got hit with even more problems and the failing of a drive...

I was editing on a drive and i don't know what happen but the entire drive is now acting like it's empty and I can repair it. used disk warrior. It just pop ups the 'format' box.

Any advice? should I just go to apple store?

Ok question and a big one.

Was the firewire adapter the one from apple or a third party adapter there are some bad adapters for thunderbolt going out that are made in china using a hacked firmware on them there not nice and constantly fail.

As for drives you would be better off using Western digital drives in a external hard drive inclosure and not a firewire one a usb one let me explain.

The downfall with firewire is when it goes wrong it corrupts the hard drive or you lose data there are other alternatives as well

http://www.amazon.com/dp/B0099TX7O4/?tag=macforums0e4-20

another warning Seagate hard drives don't play well with firewire as well you have been warned.

Two things strike me in your post; 1. I don't like Firewire to Thunderbolt adaptors they often create problems and the Thunderbolt dock you mentioned is it AC powered because if not it will have trouble running and external HD. 2. You seem to be going through a lot of HD's and I'm wondering what make of HD's and what quality they are. It seems odd that some work and some don't so unless you have an intermittent problem with your new iMac then it is the HD's I would suspect. Difficult to test this without another iMac of course but you did say some of them have even failed connected to your MBP so again I would suspect the HD's. I have read that some Korean HHD's directly off the assembly line have over 25% failure rates.