End parity check early when parity drive is larger than data drives

[audigex]

I have a 6TB parity drive and 2TB data drives (the result of a drive failing and doing a parity swap to plan for future expansion)

When running a parity check, the first 2TB completes in 8 hours or so, but then the check runs for another 16 hours checking the remaining "4TB" of the array. This seems unnecessary when the other 3 drives are spun down, there's no parity to check and it's just adding wear to my parity drive for no real reason

So yeah: wouldn't it make sense to end the parity check at this point?

[itimpi]

It is important that the remainder of the drive is reading as all zeroes so that parity remains valid when you later add larger data drives.   Skipping this check could potentially cause data loss at a later date when that happens.

[audigex]

Surely that could be handled by just zeroing the rest of the drive when adding a larger drive?

It seems pointless to spend 16 hours parity checking 4TB every month, just for a "maybe you'll want to do this one day" task that you'd need to do once... it seems like it would make far more sense to do that one-off task once, rather than doing it monthly forever?

The array already knows how big the biggest data drive is, and the new data drive needs to be zeroed anyway, so presumably those two things can be done simultaneously when necessary

Running it monthly/on every parity check when it may never even be necessary, just seems very inefficient for something we might one day do once

[-Daedalus]

I've asked for this previously as well. Context: 

I'll give another +1 here. sure there are cases that would have to be catered for, but I think given the nature of unRAID, it's a pretty natural thing that will happen. It would be nice to just have a toggle option for it with appropriate messaging. 

 

 

[piyper]

I am in favour of this as well, I would not even worry about what is on the rest of the parity drive, leave it in whatever state it/they are, you don't even really have to clear it.

Simply stop at the size of the largest data drive, then when/if a new bigger drive gets added to the array and increases the top level, simply force a parity check on the remaining portion or do a full parity rebuild if the other is not possible. (can't see why it would not be  possible)

 

in my case, my largest data drive is 6TB (soon to be 8TB), but my two parity drives are 14TB (as I am sure others do, I buy when I get a good deal), so the parity check takes much longer than it would if it stopped at the max data drive capacity.

 

As I hope, most people do a parity check on a schedule (let's say monthly), and in my case, the check takes over twice as long as it would if it would stop at the largest data drive.

I would rather do a incremental rebuild for the added top capacity every once in a while when adding a new drive  than to have my checks run for days (IMO) needlessly every month.

 

A switch might be nice to support those people that add drives frequently, however, if we can get incremental parity rebuild working, even that would not be that big of a deal (IMO).

 

Thank you

 

Edited October 18, 2023 by piyper