April 30, 201511 yr Hi guys, I've noticed that 2 of the drives in my array, both 3TB WD Greens, are now showing pending sectors. One is reporting 1 sector and the other 5. They both also report 1 for Offline Uncorrectable. I've been a bit dubious about these drives for a while (probably should have replaced them before now). During parity checks they've been throwing some read errors, which reduced when I changed and rerouted cables, but hadn't shown any sector issues until now. I am currently in the process of moving some of the files from the drives onto other drives in the array, although I don't have space for all of it, and have excluded those drives from any shares that are likely to get written to. I've got a couple of replacement drives on order which should be delivered tomorrow and I'll run a couple of preclears on each of them. Once that is done, what should be the procedure for replacing the WD drives and moving the data to the new ones? Am I best off adding the drives to the array, moving the data from the WD drives and then removing the WD drives and doing a new config?
April 30, 201511 yr Hi guys, I've noticed that 2 of the drives in my array, both 3TB WD Greens, are now showing pending sectors. One is reporting 1 sector and the other 5. They both also report 1 for Offline Uncorrectable. I've been a bit dubious about these drives for a while (probably should have replaced them before now). During parity checks they've been throwing some read errors, which reduced when I changed and rerouted cables, but hadn't shown any sector issues until now. I am currently in the process of moving some of the files from the drives onto other drives in the array, although I don't have space for all of it, and have excluded those drives from any shares that are likely to get written to. I've got a couple of replacement drives on order which should be delivered tomorrow and I'll run a couple of preclears on each of them. Once that is done, what should be the procedure for replacing the WD drives and moving the data to the new ones? Am I best off adding the drives to the array, moving the data from the WD drives and then removing the WD drives and doing a new config? Given that 2 array drives may not read properly, I think you have it about right, with adding the precleared drives (which doesn't invalidate parity) vs replacing one drive at a time which would require the second drive to be read flawlessly to reconstruct the replacement. If you encounter a read error while copying, statistically the chances of the errors on the other drive being in exactly the wrong spot are pretty low, vs the almost guarantee of a bad read while fully reconstructing a drive with parity.
April 30, 201511 yr Author I figured that adding cleared drives and copying/moving the data would likely be faster than rebuilding 1 drive at a time. I could probably even do both copies at the same time. It might also indicate what files, if any, are damaged. If during the copy it says "can't read file X" Obviously the new config, after removing the "bad" drives will require a parity build.
April 30, 201511 yr I figured that adding cleared drives and copying/moving the data would likely be faster than rebuilding 1 drive at a time. I could probably even do both copies at the same time. It might also indicate what files, if any, are damaged. If during the copy it says "can't read file X" Obviously the new config, after removing the "bad" drives will require a parity build. Theoretically if unraid encounters a read error, it will spin up all the other drives, compute what should be there from parity, and attempt to write that value back to the drive. That action will clear pending sectors if it completes successfully, or unraid will red ball the drive and not read from it any more if the write fails. So, if you get a file error while copying, it usually means file system corruption which can be caused by several different things, not a bad drive necessarily. Thinking about this some more, I wonder if you could do a dd read with the output to null to force the drive to deal with pending sectors.
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