fast IO where the red-black tree sorting CPU time becomes
significant.
-header_offset=siint Swap the verification header with data somewhere else
+verify_offset=siint Swap the verification header with data somewhere else
in the block before writing. Its swapped back before
verifying.
-header_interval=siint Write the verification header at a finer granularity
+verify_interval=siint Write the verification header at a finer granularity
than the blocksize. It will be written for chunks the
size of header_interval. blocksize should divide this
evenly.