HAMMER filesystem check / CRC verification

Tomohiro Kusumi kusumi.tomohiro at gmail.com
Fri Jan 22 07:44:29 PST 2016

(resending as i forgot to send to users at ...)

# hammer -v -f ${DEV} blockmap
# hammer -v -f ${DEV} checkmap
# hammer -v -f ${DEV} show

These three do some validation from different point of view.
If the last two lines of each output says 0 error, then no error was found
at least by what these 3 commands test for.

Note that there seems to be a bug in hammer where a valid filesystem would
still show ^B in hammer show output. I usually run some test scripts (that
contain there 3 commands) before I commit something, but I see ^B in hammer
show every once in a while. It could be that the way hammer show tests the
filesystem is missing something and results in showing errors that aren't
really errors. This occurred at least back in DragonFly 4.0 era in 2014,
and it still does on 4.4. It has been on my todo list for a long time.

2016-01-22 23:59 GMT+09:00 PeerCorps Trust Fund <ipc at peercorpstrust.org>:

> Hi All,
> In ZFS, the command "zpool status" gives a succinct overview of the status
> of mounted file systems. In particular, whether there might be checksum
> errors on files or other data structures.
>         NAME        STATE     READ WRITE CKSUM
>         tank        ONLINE       0     0     0
>           ada0p2    ONLINE       0     0     0
> In HAMMER the "show" command provides an extremely detailed output of all
> data structures and CRC verifications.
> I've used the command:
> hammer -f /dev/serno/disk-serial-number show |grep B------
> On a mounted disk and the output was clean (nothing) after running for
> some time with noted disk activity. Does this mean that all CRCs are valid?
> Are there other commands in addition to "show" that allow for validation
> and examination of data structures on HAMMER volumes?
> --
> Mike
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