Why does parity need to build on a cleared drive?

[Spies]

After preclearing the array and parity, all discs will be zeroed, so why is it necessary to build the parity?

[Helmonder]

When you add a disk it is not necessary to build parity.

 

[Spies]

I mean a brand new array/configuration.

 

If unraid can see the preclear signature, why is there still a need to calculate the parity. All discs will be zero, therefore the parity will also be zero.

[Helmonder]

But the parity has got to be MADE zero...

 

Also the disks are not complete zero since there is a filesystem with data on there.. even if there are no files.

[gubbgnutten]

But in the case were one sets up a new array, and all data disks as well as the parity-to-be have been pre-cleared, the exact contents are already known - zeros! No file systems on the data disks yet, formatting is later in the process.

[trurl]

If a clear parity and a set of clear drives are all added at the same time in a new configuration, then it should be valid to format the disks and just have parity update like normally when formatting instead of doing a complete parity sync. It has been many years since I had that scenario, so I don't know if unRAID does a parity sync anyway or not.

 

Seems like a special case that is probably not really checked for, but maybe you can manually prevent the full sync by checking the parity is valid box before starting.

[JorgeB]

If all disks are cleared, including parity(s), you can check the "parity is already valid" when first starting the array.