Hi there,

 

I intend to replace an old drive A with a bigger old drive P, where P was in use as Parity 1 and capacity(P) > capacity(A).

This would mean:

Drive P is not a new drive and full with parity "garbage".

Since P is has more than twice of the capacity of A, after replacing A and reconstructing the content of A on P, there will be plenty of "garbage" on the rest of P's capacity.

 

Does that mean than I would need to pre-clear P before I assign it to the drive slot of A, even though P is not a new drive?

 

Thanks for you help!

 

You never need to preclear a disk before a rebuild, you can if want to test it, if the old parity disk was healthy you just need to do a standard replacement.

2 hours ago, jus7incase said:

there will be plenty of "garbage" on the rest of P's capacity. 

It will automatic clear / write zero.

 

After that, each parity check duration will much longer.

3 hours ago, jus7incase said:

there will be plenty of "garbage" on the rest of P's capacity

No there won't. The file system will automatically be expanded to use the full capacity of the disk.

Just to sort of combine the 2 previous responses. When rebuilding to a larger disk, the entire disk is written to be consistent with parity, not just the amount needed for the data that was on the smaller disk. So, no garbage.

1 hour ago, John_M said:

No there won't. The file system will automatically be expanded to use the full capacity of the disk.

Extending the data disk's filesystem is to my understanding just a matter of writing a few sectors, but it will usually zero out all so far unused sectors.

I understand that I would not see that garbage in the unallocated and unused sectors.

I was wondering if the parity system would benefit if you zero out the sectors that were not reconstructed and which still contain the garbage from the old parity disk.

 

However, the current answers seem to suggest that zeroing that old parity disk before repurposing it as a data disk, even if only a fraction of it will be used to reconstruct the replaced data disk, because reconstruction will also handle the surplus capacity in a meaningful way.

 

1 minute ago, trurl said:

Just to sort of combine the 2 previous responses. When rebuilding to a larger disk, the entire disk is written to be consistent with parity, not just the amount needed for the data that was on the smaller disk. So, no garbage.

Thanks that made it very clear to me and I wont preclear the old parity disk before using it to replace the old data disk.

 

Thank you all for being so fast and helpful!

40 minutes ago, trurl said:

the entire disk is written to be consistent with parity

If you think about it, it couldn't be otherwise or parity would be invalid.