How can I avoid having to preclear a drive for array that was already a parity drive for a year

[andyd]

this drive does not need preclearing and these steps make it sound like it needs to happen...
 

https://wiki.unraid.net/UnRAID_6/Storage_Management#Adding_disks

[Frank1940]

You don't have to 'preclear' any drive to add it as a new data drive to the array.  (Today, Preclear is mostly used to test the drive to detect infant mortality failures.)  Unraid will 'clear' it and then format it.  When these two steps are done, parity will be correct and the new data drive will be available for use. 

 

IF this is confusing to you, I have a question for you.  Why do you think this drive does not need to be cleared?

[andyd]

Sure, I took preclear to mean clear because of the several hours comment. Since the guide doesn't give an estimate, I assumed it was going to be a multi day thing as it is for preclearing. i wouldn't have expected adding a new drive to an array to be a 10+ hour process which is what I'm seeing now but I'll look into why that is the case

 

 

 

Edited April 15, 2020 by andyd

[Frank1940]

The time required depends on drive size.  What it is doing is writing zeros to every byte on the drive first.  Then it will add the drive to the array and formatted the disk which will update parity.  The drive will then active on the array with parity being correct.  All of those zeroed bytes on the valance of the disk guarantee that.  (The other software design option would have been to added the drive to the array as is and then format the drive.  Then update parity because there are non-zero bytes on that disk from its earlier life.  You do realize that formatting a disk just adds a empty file system to a disk.)

[trurl]

Note that clearing a drive only has to happen when adding a disk to a new slot in an array that already has valid parity. This is so parity will remain valid, since a clear disk is all zeros and those zeros have no effect on parity.

 

When using a disk to replace another disk in the array, it does not have to be clear since it will be completely overwritten from the parity calculation and thus will be consistent with the existing parity.

[andyd]

On 4/15/2020 at 9:43 PM, Frank1940 said:

The time required depends on drive size.  What it is doing is writing zeros to every byte on the drive first.  Then it will add the drive to the array and formatted the disk which will update parity.  The drive will then active on the array with parity being correct.  All of those zeroed bytes on the valance of the disk guarantee that.  (The other software design option would have been to added the drive to the array as is and then format the drive.  Then update parity because there are non-zero bytes on that disk from its earlier life.  You do realize that formatting a disk just adds a empty file system to a disk.)

 

On 4/15/2020 at 9:58 PM, trurl said:

Note that clearing a drive only has to happen when adding a disk to a new slot in an array that already has valid parity. This is so parity will remain valid, since a clear disk is all zeros and those zeros have no effect on parity.

 

When using a disk to replace another disk in the array, it does not have to be clear since it will be completely overwritten from the parity calculation and thus will be consistent with the existing parity.

Got it. Thanks guys for the explanations. That's helpful!

 

Server now where I wanted it to be and now also have a better understanding of how Unraid works