Here's the dbuf we're currently reading:
     966f200::dbuf
addr object lvl blkid holds os
966f200 4 0 0 1 ztest/ds_3
     966f200::print dmu_buf_t db_data
db_data = 0x9ae0400
     0x9ae0400/10J
0x9ae0400: c1c7ced932020d c1c7ced932020d c1c7ced932020d c1c7ced932020d
c1c7ced932020d c1c7ced932020d c1c7ced932020d c1c7ced932020d
c1c7ced932020d c1c7ced932020d
The pattern we're expecting is actually this: a34ae10b5f2db2. If we attempt to
read the block on disk we find that it has matches what ztest_ddt_repair()
would have written:
     ~c1c7ced932020d=J
ff3e383126cdfdf2
     966f200::print dmu_buf_impl_t db_blkptr | ::blkptr
DVA0=<0:71d3c00:800>
[L0 UINT64_OTHER] SHA256 OFF LE contiguous dedup single
size=400L/400P birth=55L/55P fill=1
cksum=18486450d3ce8c6d:75a72f4bbf117b0f:2d3a226314eb5650:2eb0fd68648b1af0
   1. zdb -U /rpool/tmp/zpool.cache -R ztest 0:71d3c00:800 | head
      Found vdev type: mirror
0:71d3c00:800
0 1 2 3 4 5 6 7 8 9 a b c d e f 0123456789abcdef
000000: ff3e383126cdfdf2 ff3e383126cdfdf2 ...&18>....&18>.
000010: ff3e383126cdfdf2 ff3e383126cdfdf2 ...&18>....&18>.
000020: ff3e383126cdfdf2 ff3e383126cdfdf2 ...&18>....&18>.
000030: ff3e383126cdfdf2 ff3e383126cdfdf2 ...&18>....&18>.
000040: ff3e383126cdfdf2 ff3e383126cdfdf2 ...&18>....&18>.
000050: ff3e383126cdfdf2 ff3e383126cdfdf2 ...&18>....&18>.