New 10TB HDD fail after 342 hours and other concerns


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My "parity sync / data rebuild" isn't working the way I thought it would.

I disabled parity sync before loading data onto my two replacement 10tb data disks and then started the parity sync.  I observed that during the sync it has only been reading from the parity disks and only writing to the replacement data disks, both of which have the "device contents emulated" flag. 

 

That's the behavior I expected if I'd added the disks and immediately performed a data rebuild, but since I added data to the disks and then clicked the Sync button, I was hoping it would be updating the parity disks, not the data disks.

 

Obviously I was wrong.

 

Was there a way to force it to behave the way I was expecting?

The only thing I can think of is that I could perhaps have removed the parity disks from the Unraid configuration so it wouldn't even think a data rebuild was possible.

 

Note that in my specific case the "data rebuild" function is a waste of time because the data from the missing data disks was also not on the parity disks (see earlier posts in this thread if interested in what I did wrong to make that happen).

 

[Looks like I'll end up with both replacement data disks blank, because the parity drives thought the disks they replaced were blank.  Fortunately, I can copy the data to the array again once this is complete.  Doesn't look like I lost very much yet due to the increasing reallocated sector count.]

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It's somewhat unclear to me what you did exactly. "Disable parity sync" doesn't really make sense. Parity sync is when you build parity. And there is also no way to disable parity updates which is probably what you were trying to accomplish with whatever you did.

 

Usually replacing a data disk means assigning a disk to the same slot as a previous disk so you can get Unraid to rebuild the contents of the original disk onto the replacement disk using the parity calculation. But reviewing the thread I see that there is no data to rebuild.

 

Let's just go forward from here.

 

If your array has a parity disk assigned, and you want to work without parity, you must New Config without a parity disk assignment.

 

Go to Tools - New Config and Retain All. Then you can assign any disks however you want. As long as you don't assign a data disk to the parity slot nothing will be changed on any of the disks. Also, before you ask, New Config doesn't change any of your other settings, only your disk assignments.

 

Just assign your disks including the "replacements" and leave the parity slot unassigned. Then start the array and you will be able to work without parity.

 

When you are ready for parity again, stop the array, assign the parity disk, and start the array to begin parity sync.

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19 hours ago, trurl said:

It's somewhat unclear to me what you did exactly. "Disable parity sync" doesn't really make sense. Parity sync is when you build parity. And there is also no way to disable parity updates which is probably what you were trying to accomplish with whatever you did.

What I actually did was cancel the parity sync.  

Thanks for your instructions on how to properly do what I was trying to do in delaying the parity build till I had completed my manual reloading of data.

 

Meanwhile, I'm very happy to report that all the data I'd copied to the replacement disks is still there after the parity sync completed.  That makes me wonder why the Main tab showed only data writing to those disks and only reading from parity disks when it seems it should have been the reverse.

 

Thanks to all of you who helped me deal with these disks!

I'll be sure to pass on the knowledge.  There are a few organizations in my community which could really benefit from an Unraid!

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15 minutes ago, Wolfe said:

I'm very happy to report that all the data I'd copied to the replacement disks is still there after the parity sync completed.  That makes me wonder why the Main tab showed only data writing to those disks and only reading from parity disks when it seems it should have been the reverse.

This part is unclear also since you don't say whether or not you actually followed my instructions on removing parity from the array.  If you just continued on with what it was already doing, then it rebuilt the empty disks (not a parity sync), and you wrote to them while it was doing the rebuilding.

 

The rebuild of the empty disks would involve writing to the rebuilding disks by getting the data (even though the disks where "empty") from the parity calculation by reading parity and all other disks. So there would be a lot of writes to the rebuilding disks and a lot of reads from parity and all other disks.

 

And there is no reason you can't write to a rebuilding disk, though it will slow things down somewhat since the rebuilds and the writes would be competing for the same disks.

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