Parity check after adding new disk

[tucansam]

After adding a new disk and rebuilding the disk, is it necessary to perform a parity check?  Is it redundant?  A good idea?  Best practice?  I've always done one, but not sure its necessary.  

 

Thanks.

[trurl]

2 hours ago, tucansam said:

After adding a new disk and rebuilding the disk, is it necessary to perform a parity check?  Is it redundant?  A good idea?  Best practice?  I've always done one, but not sure its necessary.  

 

Thanks.

I have a quibble with your first sentence. Adding a new disk would mean a new slot in the array, which does not involve a rebuild. I think what you mean is replacing a disk with a new disk.

 

A non-correcting parity check after the rebuild will check that the rebuilt data is correct.

[JonathanM]

Adding a disk to a new array slot or rebuilding/replacing a disk are two separate actions.

When adding a disk, a correcting parity check is a good idea, but not necessary.

After rebuilding a disk, a non-correcting check ensures the rebuild was accurate.

Parity checks should always return exactly zero errors, any other result should be investigated.