Getting millions of parity sync error

[clovercake]

Had a unclean shutdown a few days ago, performed parity check and got 700m+ errors.

Executed the parity check again, while expecting 0 errors, it still split out 400m+ errors at 80%. :(

tower-diagnostics-20220807-2248.zip

[Squid]

Your second result is to be expected because your first one was more than likely a non-correcting check which means that the second one will give the exact same result.

 

The question though is why on the first one you're getting the millions of errors.  Did you change drives or anything between 7/17 and 8/6?

[clovercake]

51 minutes ago, Squid said:

Your second result is to be expected because your first one was more than likely a non-correcting check which means that the second one will give the exact same result.

 

The question though is why on the first one you're getting the millions of errors.  Did you change drives or anything between 7/17 and 8/6?

I did added 2 new drives on 7/15, but nothing between 7/17 ~ 8/16. 

[trurl]

How did you add those?

[clovercake]

1 minute ago, trurl said:

How did you add those?

Added the first drive via the parity swap procedure (new drives are larger than the parity drive). Rebuilt parity.

Then added in second drive. Rebuilt parity.

[trurl]

2 hours ago, clovercake said:

Added the first drive via the parity swap procedure (new drives are larger than the parity drive). Rebuilt parity.

Then added in second drive. Rebuilt parity.

We should start by clearing up verbage.

 

"Add" means a new slot in the array. Parity swap would not be an "add". It is a slightly more complicated variation of "replace"

 

So what do you actually mean when you say you "added in second drive"? Was this a new slot? Or do you actually mean you replaced an existing drive?

[clovercake]

6 hours ago, trurl said:

We should start by clearing up verbage.

 

"Add" means a new slot in the array. Parity swap would not be an "add". It is a slightly more complicated variation of "replace"

 

So what do you actually mean when you say you "added in second drive"? Was this a new slot? Or do you actually mean you replaced an existing drive?

Sorry for the confusion.

 

I bought two new drives (16TB).

Replaced (Parity swapped) the parity drive (10TB -> 16TB)
Then, added a new slot in the array for the second 16TB drive.

[trurl]

I am thinking you somehow invalidated parity.

 

So, lets make sure we understand parity swap.

 

In addition to replacing parity, parity swap means you also replaced a data drive with the former parity drive, all as part of one procedure. Parity swap copies parity to the larger disk then rebuilds the replaced data drive to that former parity drive. Is that what you actually did?

 

Parity swap really isn't necessary unless you already have a failed data drive. If not, you can simply replace parity with a larger parity using the normal replace drive procedure. Then, if you want to, you can reuse the former parity drive to replace a data drive using the normal replace drive procedure.

[clovercake]

3 hours ago, trurl said:

I am thinking you somehow invalidated parity.

 

So, lets make sure we understand parity swap.

 

In addition to replacing parity, parity swap means you also replaced a data drive with the former parity drive, all as part of one procedure. Parity swap copies parity to the larger disk then rebuilds the replaced data drive to that former parity drive. Is that what you actually did?

 

Parity swap really isn't necessary unless you already have a failed data drive. If not, you can simply replace parity with a larger parity using the normal replace drive procedure. Then, if you want to, you can reuse the former parity drive to replace a data drive using the normal replace drive procedure.

> Parity swap copies parity to the larger disk then rebuilds the replaced data drive to that former parity drive. Is that what you actually did?

Yes. Didn't realized there's a normal replace drive procedure, therefore went with the parity swap.

 

Disk 1 (Old Parity) -> Data Drive
Disk 2 (New Drive) -> Parity

Disk 3 (New Drive) -> Data Drive

[JorgeB]

Parity swap is known to sometimes, unclear yet why this happens only in some cases, no correctly zero out the extra parity capacity, so the first check will correct that.

[trurl]

7 hours ago, clovercake said:

Didn't realized there's a normal replace drive procedure, therefore went with the parity swap

How did you find out about parity swap, a google search? The normal replace drive procedure is in the documentation before the parity swap procedure:

https://wiki.unraid.net/Manual/Storage_Management#Replacing_disks

 

Maybe another case where the term "parity swap" just confuses people, since they think they know what it means, and what they think it means is what they want to do. The old "swap disable" terminology, nobody knew what it meant, but at least they didn't think they knew what it meant.

[trurl]

Older docs:

https://wiki.unraid.net/The_parity_swap_procedure

Quote

This page describes how to do the 'Parity Swap' procedure, often known as the 'Swap Disable' procedure.

Historically, it was better known as the 'Swap Disable' procedure, probably because it requires the data drive to be disabled first, then involves a swap of the parity drive, the disabled drive, and the new replacement drive. Perhaps it should be called the "3 drive parity shuffle"?

 

[clovercake]

On 8/8/2022 at 3:54 PM, JorgeB said:

Parity swap is known to sometimes, unclear yet why this happens only in some cases, no correctly zero out the extra parity capacity, so the first check will correct that.

Looks like this is the prob. Got 0 errors on the 3rd parity check.