Fast re-attach of detached device #17881
Description
Describe the feature you would like to see added to OpenZFS
When a disk is attached to another device, it is completely overwritten. While this is the right thing to do for newly attached disks, it is vastly suboptimal when a disk is re-attached to the same device.
As the ZFS label is not cleared from the detached disk, and having the DTL already tracking the required information, it should be possible to resynchronize from the source disk only the changed data.
Linux MD RAID provides this very same feature - see mdadm --re-add behavior (which is even implied by a plain --add).
How will this feature improve OpenZFS?
Re-attaching a disk will be much faster, potentially avoiding TBs of reads/writes.
Additional context
None.