Forcing a full file read in ZFS even when checksum error encountered

[Steven Hartland]

----- Original Message ----- 
From: "Artem Belevich" <art at freebsd.org>
> Maybe. See here:
> http://blogs.oracle.com/relling/entry/holy_smokes_a_holey_file
> 
> Using that method you still would not get the bad block, but you may
> be able to recover data beyond it.
> 
> If you really want to get access to the data that ZFS considers to be
> corrupted, you need to get close and personal with zdb.
> This blog post may be a good starting point: http://cuddletech.com/blog/?p=407

Perfect, thanks Artem.

For the record using the following zdb commands I've managed to get the
file data off the pool.

1. zdb -dddd <pool>/<dataset> (find the objectid by searching for the
filename)
2. zdb -ddddd <pool>/<dataset> <objectid> (find the indirect blocks, the
third block of hex)
3. zdb -R <pool>:<indirect blocks> 2>/tmp/filedata

e.g.
zdb -dddd tank/usr
zdb -ddddd tank/usr 1243
zdb -R tank:0:22df120000:18000:r 2>corrupt.jpg

    Regards
    Steve



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