I have a Seagate 500gb Barracuda 7200.10 ...

To be specific, it's the ST3500630AS.

The drive is 3 years old and up until about a month ago was working fine. It doesn't really make any clicking noises out of the ordinary, although it does make a certain click that it didn't used to in my memory...

I'm thinking head crash, personally...though I was able to pull all but 4 of my files off of it, ~350gb recovered.

The symptom is that while plugged in, it will inexplicably and randomly disappear from the bios/os, regardless of whether it's mounted or not. I use Linux, and so I know it's not some OS error. It worked fine up until now, so I know it's not the bios. I have tried it on multiple machines as well.

I've tried testing with SMART and it has plenty of errors...I'll post the pastebin of that below:
http://pastebin.com/3TzTCtL0

That said, you think it's worth pursuing repair? I've gotten 2x 1TB drives since then...but I really want to figure out what went wrong.

It would seem that to disappear from bios/os i would have to go not ready. It is a little hard to say without further testing but I would suspect a PCB problem. These drives have a serial diagnostics port. Withthe correct adapter you may be able to learn something about what is happening.

_________________
HWHacker
Smiles

It is worth pursuing a repair if that is what you want to do for the purpose of learning a bit about your HDD.

It is not worth pursuing a repair if there is a warranty on the drive that you can claim under. It is certainly not worth the time and energy if you just want your drive to be usable again. There is a reason it failed and even if that reason can be resolved, often it is down to a problem that will reoccur.

No. You are fortunate to have your data so just be happy and throw this in the trash.

Smart errors, drive goes offline, ID's in BIOS on start-up.

Almost 99% dead certain it is not pcb.

Almost dead certain start of media failure.

do what hddguy wrote.

I think you ave to be a new one. It's already gone and It is worth pursuing a repair if that is what you want to do for the purpose of learning a bit about your HDD.