No one's ever taken a disk apart ? I'm ashamed of youse guys ...
Mighty Casey has struck out but did learn some stuff :
In this case, I was barking up the wrong tree from the very beginning : the disk that failed was a high-quality enterprise-grade 15k Fujitsu scsi disk that only had a year or two of service. It dates from 2006 but hadn't been used much. it was working fine when I shut the computer off, then never showed up the next time it was booted.
Smart first move would be to run fx against it. Unfortunately, as a boot disk and the only 80-pin sca disk I had, this was impossible. I got totally off on the wrong tangent trying 68 pin disks, cables, dismantling the board that the disks plug in to, etc etc. I kept assuming that it was just a corrupt filesystem and put all my efforts into the wrong places until I finally got a second adapter card installed and tried an fx against that disk
separate
from the boot controller. Oops.
If you have a second way to access a disk, that's a
big
help in diagnosis. Another SGI or a Loonix box that can read xfs would do. I put too much trust in the fact that this disk had been fine when shut down and made no bad noises. fx is your friend.
The basics are readily available by search but here's what I noticed :
If you are lucky, this isn't anything to be afraid of. All those "oh noes ! you will instantly destroy your disk if you open it !" pronouncements are bullshit. Yes, it for sure won't last five years after opening. But it's already dead. Don't be a baby, all the parts are made in non-clean-room environments. They aren't vampires, exposure to the sun won't melt them into a blob on the floor.
If you are lucky, a logic board swap will fix the problem. It's easy. Yay.
If that doesn't work, I'd consider pulling the cover off and powering the disk up in the open. I didn't do this and ended up chasing the wrong rabbit because of it. I
thought
the disk was spinning up because the case got warm. In fact, it wasn't. Swapping out the heads when the problem is the motor is not going to fix anything.
With the cover off, you can see that the disks don't spin up until they are addressed. I always thought they spun up at power-on but no. You can watch the bootup terminal display; when the process gets to each adapter,
then
the disks are powered up. Not sure if this is true for the boot disk but observed it on a secondary adapter.
Next step would be to swap out the heads. This is not so difficult. I used strips of paper to slide them off the platters without crashing. That was pretty tacky but it worked. Six hands like those Indian godesses would be a help. The twenty-six boobs, not so sure about.
The magnet is very strong, when you first remove it it will surprise you and try to leap at the disk, bringing about instant destruction. Be prepared.
Replacing the heads is actually pretty simple but decent tools would be a help. Toothpicks, pieces of paper, melted soda straws do not count
All that work and the thing still didn't show up, crap. So I took the cover off and viola, the disk wasn't spinning. Oh phooey. This is why I mention taking the cover off early in your crusade might be smart. I think swapping the heads an extra time was not an aid to successful surgery in my case.
If you have a single platter, swapping it would be easy. If you have two or more, you're screwed. They need to be timed but there is no physical feature doing this. I looked online, there are platter-removing tools but the ones I saw were very expensive pieces of crap. $ 300 for a tin can with two screws ? those guys must be crazy. If the data were important you could make a decent tool - maybe even with a 3d printer
Otherwise draw something up and have the local shop mill it out for you out of delrin. My unbacked-up data was just some customizations I had done to the desktop and some emails that are stored offline anyhow. Of course I can't
get
to offline because the gfw has it blocked but that's a different problem. In this case, I just knocked out a crappy little thing to try to hold the platters in time to each other. Didn't work very well but if you have fairly immportant data, it should be easy to accomplish.
Swapping the platters is even easier than swapping the heads (except you have to get the heads out of the way anyhow.)
In conclusion ... this didn't work for me but that was because I had crappy tools, made some wrong conclusions, and wasn't
that
concerned about the data. If the data was important but not important enough to spend a ton of money on recovery, chances are good you could do it. And the clean room thing is hogwash. Sure, for a disk to last five years you'd need that. But to run foir twenty minutes while you get most of your files, don't be silly. A can of air and a reasonably clean environment wll work fine. Cleanliness is not the biggest problem. In fact, running the disk open will tell you a lot about what's broken, before you waste time and effort and potentially breaking something that isn't the problem. Dealing with very tiny, very fragile parts is the biggest trouble. And keeping the platters timed to each other,
thats
the biggest problem.
btw, a data recovery service .... this isn't as difficult as they make it out to be. If it's a physically bad disk that isn't crashed or damaged, and it's not a file-system problem, getting the data off should be doable for a careful amateur. There's gold in them thar hills.
