[SOLVED] Data Rebuild

[JPilla415]

Diagnostics attached.

 

I had an older drive that I wanted to replace with a larger drive and I am worried that I did things slightly out of order. Before starting, I backed up my usb drive.

 

1) I stopped the array.

2) Powered down

3) Replaced the hard drive

4) Turned on the system

5) Assigned the new drive in the slot of the old drive

6) Started the array

 

The rebuild process never started and the disk contents were being shown as emulated. So, I stopped and powered down the array. I booted back up the array to take diagnostics, but have taken no further steps. What is the best course of action? I was running a bit on auto-pilot and followed the old instructions for v4: https://wiki.unraid.net/Replacing_a_Data_Drive

tower-diagnostics-20200514-1611.zip

[JPilla415]

After searching around, it seems that I could revert to a backed up USB drive and put the OLD disk back in place and then start the whole process over. That seems like quite a bit of effort.

 

Could I just manually start a parity check - would that rebuild the drive?

[trurl]

2 hours ago, JPilla415 said:

1) I stopped the array.

2) Powered down

3) Replaced the hard drive

4) Turned on the system

5) Assigned the new drive in the slot of the old drive

6) Started the array

This should have worked assuming you haven't left anything out of your description. You didn't New Config at any point did you?

 

2 hours ago, JPilla415 said:

The rebuild process never started and the disk contents were being shown as emulated.

If you remove the original disk it will be emulated, and if you replace it with another disk and start the array, it will still be emulated while it rebuilds. If instead you put the same disk back in, and you never started the array with that original disk unassigned or any other disk assigned to the slot, then it would just take the disk as is since it is the same disk and it was never disabled.

 

I am just trying to suggest possible scenarios to see if it will help you remember anything you left out.

 

The syslog in the diagnostics only goes back to the last reboot, and since you rebooted after whatever you already did, there is nothing in the syslog about that.

 

Was it disk3 you were trying to replace? The last inventory in that syslog has nothing assigned to that slot.

[JPilla415]

Thanks so much for weighing in and helping out.

 

I definitely did not create a new config.

 

I am trying to replace Disk 3.

 

When I first powered on the system after replacing Disk 3, I saw a warning that Disk 3 was missing (4TB drive). I then assigned my new drive (8TB) as the new Disk 3. I clicked the "Start" button, which indicated that it would bring the array online and start a parity check and/or rebuild.

 

The array came online, and I waited ~20 mins but the rebuild never started, so I stopped the array.

 

 

[JPilla415]

To clarify, I didn't unassign the original disk 3 before powering down the system. I started the system with the disk removed and the new 8TB in it's place. Assigned the new drive, and then started the array. Based on my reading of this wiki (https://wiki.unraid.net/Replacing_a_Data_Drive), I missed step 2.

 

I also did not have to check the "Yes, I'm sure checkbox" before starting the array.

 

[trurl]

Step 2 is not really needed if you are replacing the disk. Assigning a different disk to the same slot should be enough to get it to let you rebuild.

 

Why are you running such an old version?

 

WDC WD80EFAX-68KNBN0 shows up but is not assigned. Is this the disk you intended to rebuild to?

[JPilla415]

This version has been super stable and I just never got around to updating... I kinda figured, why mess with a good thing? No other reason beyond that.

 

Yes, WDC WD80EFAX-68KNBN0 is the drive I was trying to rebuild to.

[trurl]

Assign the disk and start the array. Then post a screenshot of Main - Array Operation.

[JPilla415]

Thanks again for the help.

 

FYI, in case it matters. I started in Maintenance Mode.

 

EDIT:

Edited May 15, 2020 by JPilla415

[trurl]

33 minutes ago, JPilla415 said:

This version has been super stable and I just never got around to updating... I kinda figured, why mess with a good thing? No other reason beyond that.

Many plugins may not be compatible with your old version. But your plugins are old too. Diagnostics for that old version doesn't have some of the useful information provided by later versions. There have been a number of fixes since that old version also. Possibly your old version even has a broken version of the XFS repair which might bite you if you have to repair the filesystem on a disk.

[JPilla415]

Ah, well, that's a great reason to upgrade then. As soon as I can get this current array stable and safe, I'll upgrade. Thanks for the heads up.

[trurl]

4 minutes ago, JPilla415 said:

FYI, in case it matters. I started in Maintenance Mode.

I've never done that or seen anyone else do it when they are trying to rebuild a disk. It might work if you pressed the Sync button (at least according to the description), but I would be more familiar with what is happening if you started it in normal mode. And I don't know why you would want to do it in Maintenance mode anyway. I don't see how that would be any safer than doing it the normal way.

 

Just start it in normal mode and post another screenshot.

[trurl]

And you still have the original disk (I assume) in case something doesn't work out for some reason, so all the files are still on that original disk.

[JPilla415]

I was trying to play it as safe as possible, keep the array in the exact same state, so that I could always load back in my old data disk and USB config in case I had a disk failure during the re-build. Things seem fine now, as soon as I started the array in normal mode the rebuild fired off on its own. I guess if you're in Maintenance Mode, the data rebuild doesn't start automatically, as per the wiki. That paired with my missing "step 2" in the wiki, had me concerned.

 

Edited May 15, 2020 by JPilla415

[JPilla415]

8 minutes ago, trurl said:

And you still have the original disk (I assume) in case something doesn't work out for some reason, so all the files are still on that original disk.

Yes, I still have the original disk. That was part of my thinking of using Maintenance Mode. I was just trying to ensure the rest of the array remained identical.

[trurl]

2 minutes ago, JPilla415 said:

That was part of my thinking of using Maintenance Mode. I was just trying to ensure the rest of the array remained identical.

OK, I guess that makes sense. Since the disks aren't mounted nothing can be written to the array, and parity stays the same while the disk rebuilds. At least that is how it seems to me it should work. I just don't know for sure it does work that way.

 

Maybe @johnnie.black will comment on this thread tomorrow and tell us. He seems to have tested everything.

 

Anyway, even if you did allow writes and parity updates during rebuild, you could always put the original disk back and rebuild parity.

[JPilla415]

1 hour ago, trurl said:

Anyway, even if you did allow writes and parity updates during rebuild, you could always put the original disk back and rebuild parity.

That's a great point.

 

Well, data rebuild is at 10% and things look alright so far. I really appreciate the assistance earlier.

[JorgeB]

Fine to rebuild in maintenance mode, just need to press sync to kick it off.

[JPilla415]

Well, that's good to know going forward. I feel silly having asked for help over something so simple. Again, I was just thrown off by my missing a step in the official instructions, and the rebuild not kicking off on its own. I thought those two facts combined spelled bigger problems.

 

Is it worth updating the wiki with a note about Maintenance Mode? Is that something I can contribute to or does it take a moderator?

 

Thank you both for the assistance and clarification.

 

[trurl]

7 hours ago, johnnie.black said:

Fine to rebuild in maintenance mode, just need to press sync to kick it off.

Of course this means your array is offline until done and you start normal so many would not want to do it that way. Interesting that I have never seen this done or recommended.

[JorgeB]

3 minutes ago, trurl said:

Interesting that I have never seen this done or recommended.

It's not a common thing but I've seen some users who usually do it like that, it's safer in case a different disk fails during the rebuild since you can use the old disk and parity will still be 100% in sync, it won't be just by starting the array normally, even if no other changes are done, and while this is usually not a big deal if you need to use the invalid slot with xfs disks it will be with btrfs disks, since they have a transaction ID and just by doing a single mount it will be out of date with the old disk.

[JPilla415]

That is what I had come to understand. I know data rebuilds can put more stress on disks than day to day use (at least in my case), and I like to play it safe when rebuilding. I only have one parity drive at this time, and until I have dual parity set up I don't mind the system downtime if it helps to de-risk things.

 

Good to know that manual intervention is needed to start the rebuild when in maintenance mode. I didn't recall that being necessary in the past, but it is completely possible that I am forgetting.

 

Thank you both for the feedback. Please feel free to mark this as solved.

[JorgeB]

11 hours ago, JPilla415 said:

I didn't recall that being necessary in the past, but it is completely possible that I am forgetting.

You are right, that behavior was changed not that long ago, but don't recall exactly when, tagged solved.

[trurl]

13 hours ago, johnnie.black said:

You are right, that behavior was changed not that long ago

Maybe that's why I never noticed anyone rebuilding that way, because they never had a question about how to start the rebuild.