February 9, 201511 yr I have a 4TB drive that I'm trying to remove from my array. The drive was un-mounted and I was running dd to zero the drive first so I could remove it without losing parity. Tonight, before the dd operation could finish, I had a power outage. I restarted the server and after starting the array I noticed that the drive I was zeroing now shows as unformatted. A parity check is running right now because the server detected an unclean shutdown. My question... After the parity check is finished should I be able to remove an unformatted disk from the array without affecting parity? My concern is that I'm certain the drive was not completely zeroed.
February 9, 201511 yr Community Expert No - you cannot safely remove a drive in the way you are talking about without affecting parity unless it has been completely zeroed. The fact that it is showing as unformatted just means that the initial part of the disk no longer contains a valid file system. The other possibility is to do a 'new config' and omit the disk and then rebuild parity from the remaining disks. However until parity is rebuilt you are running unprotected.
February 9, 201511 yr As long as you're running a correcting parity check, you don't need to rebuild parity -- once the check is complete, parity will be fine. HOWEVER ... as itimpi noted, you can NOT remove the drive at that point without rebuilding parity, as it is NOT all zeroes at this point. Your options are either to do a New Config and let it do a new parity sync; or rerun the dd command to zero the drive; and THEN you can do a New Config with "Trust Parity", since parity will be fine at that point.
February 9, 201511 yr Author Thank you for the answers. I understand very well now. I restarted the zeroing process. I guess it's a good thing that I lost power. Before, dd was running at about 3Mib/s and the ETA was 300 hours. After the restart dd is now running at about 20Mib/s and the ETA is under 60 hours.
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