trurl Posted March 3, 2021 Share Posted March 3, 2021 15 minutes ago, Scott A said: Only other thing would be if the parity disk still has something which seems doubtful and not sure how I would see that. Parity contains no data. Parity is a common concept in computers and communications. It is basically the same idea wherever it is used. Parity is just an extra bit that allows a missing bit to be calculated from all the other bits. Parity by itself can recover nothing, it needs all the other disks. And what you can recover from parity is what you have already seen. 17 minutes ago, Scott A said: It's almost like the parity for the failed disk got erased as well... I already explained this. When you formatted the disk, parity was updated so that it agreed that the disk had been formatted. So rebuilding after you formatted the disk can only result in a formatted disk. NEVER format a disk that has data on it you want to keep. That is why I warned you 18 hours ago, trurl said: If you format you will lose all that data. You need to repair the filesystem. Many people seem confused about format. They have some vague notion that you must format a disk to get it ready to use (whatever that might mean). Format means "write an empty filesystem to this disk". That is what it has always meant in every operating system you have ever used. Any write operation in the parity array updates parity so everything stays in sync. Format is a write operation. When you formatted the disk parity was kept in sync with that write operation. How could it be otherwise? Quote Link to comment
Scott A Posted March 3, 2021 Author Share Posted March 3, 2021 (edited) Constructor, Thank you for the above information. Again, I didn't format the original disk. I still have it. I did put in a new disk and tried to rebuild which produced nothing...funny that the rebuild ran but nothing came of it. I couldn't access the missing data and the new drive still said unformatted. Therefore I formatted the new disk. As you said, parity stayed in sync so that would have blown away what was there I guess. That leaves me likely with the only recourse is to see whether the original "bad disk" has the data still on it and I can access it on another pc as you also mentioned. All that said, when one of the disks fails in the array then as I understand it, the array uses the remaining disks and the parity disk to recreate the failed disk contents. Correct? If two disks fail then, of course, that wouldn't be possible. In my case I only had one disk fail so i still don't know how or why parity got out of sync initially before this format. Again, I appreciate the help and guidance. Edited March 3, 2021 by Scott A Quote Link to comment
trurl Posted March 3, 2021 Share Posted March 3, 2021 8 minutes ago, Scott A said: Constructor, Newbie, 8 minutes ago, Scott A said: the new drive still said unformatted. Therefore I formatted the new disk. You should have tried to repair the filesystem instead of formatting. 19 hours ago, trurl said: If you format you will lose all that data. You need to repair the filesystem. Quote Link to comment
trurl Posted March 3, 2021 Share Posted March 3, 2021 10 minutes ago, Scott A said: In my case I only had one disk fail so i still don't know how or why parity got out of sync initially before this format. Not clear parity was ever out-of-sync. You had an unmountable disk (corrupted filesystem). When you rebuilt to a new disk it was still unmountable. Probably parity was in-sync with that unmountable disk. 12 minutes ago, Scott A said: I can access it on another pc Only if that other PC is Linux. And it will likely still need filesystem repair. All of this would be so much easier if you would upgrade, you wouldn't even need another PC. Quote Link to comment
trurl Posted March 3, 2021 Share Posted March 3, 2021 1 hour ago, Scott A said: use RSTool to see if I see anything on the old disk. Not familiar with that and google doesn't help. Quote Link to comment
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