Recently my terastation NAS had a hard drive failure, and I was stuck for days trying to fix it. If you have been using the buffalo NAS for awhile, you are probably aware that it's pretty much awful. The documentation is usually hard to find, and sparse. What little information is there is frequently outdated, or just plain wrong.
This leaves users with google and a lot of forum crawling to fix issues.
After doing quite a bit of this myself, I have combined the solutions that worked for me along with what seemed to help other people and put them all here. So, for your convenience:
The LEDs
I never really found good information about these, but from what I gathered they reflect what you think they should. Green is good, red is bad. When one of my drives failed, the drive was a solid red color. When I replaced it and the NAS was trying to do something, it was blinking red.
One thing I did find online that you should watch for is that if a drive fails, depending on your array setup, it may push all your other drives over the capacity warning level. This will cause more drives to have a solid red light, making you think they are bad as well. When in reality they are just handling the data from the failed drive and almost full, which is indicated by a solid red light.
The Replacement Drive
The instructions I found online said to simply remove the bad drive, swap in the new one, and hold down function for ~3 seconds until you hear a beep. If you are lucky this will work for you, I tried this first, and the LED started to blink, but then nothing happen. The tiny display on the NAS didn't give me any information other than a drive had failed, and the web gui didn't mention anything was happening.
It can take upwards of 24 hours to rebuild the array, so I let it blink away until the next day, but nothing happen.
This leads me back to the hard drive itself. There are a few things that caused issues for people, first of which is the replacement drive being partitioned or otherwise having data on it already. This is bad and can stop the NAS from using the drive.
To fix this, hook the drive up to a computer and run some disk maintenance on it and make sure it's a clean hard drive. While you are doing this, make sure the drive is set to be dynamic, not basic. Mine was set to basic, which turned out to be the core of my issue.
Another thing to look for is the jumper on the drive depending on which brand you have. A number of people had to use a jumper on their drive set to Cable Select. Their old drive didn't have it set that way and worked, but this fixed the issue for them.
After all this I set my drive back into the system, held down function for ~3 seconds and the lights started to blink again. This time however, when I logged into the web gui, I get an alert saying that it is changing the array with a progress counter.
The System
Overall the web gui seems to be the place to go to make sure something is happening. While this is not clearly documented anywhere, flashing lights don't seem to ever spit out errors beyond the disk is broken. When you have correctly started a rebuild of your disk, the web gui will update.
One last thing to watch for with regards to the gui itself, you may need to do a cache refresh to see the latest settings / notifications. Your shares will still be available while the system rebuilds itself, but it will slow down.
It all sounds pretty simple, but the risk of breaking the temperamental system was unnerving to me especially when combined with very little useful information about how to resolve the issue, and not knowing what feed back to expect from the system when things were happening.
