HAMMER filesystem check / CRC verification

PeerCorps Trust Fund ipc at peercorpstrust.org
Fri Jan 22 11:01:17 PST 2016

Thank you. These are quite useful.

On 01/22/2016 05:57 PM, Tomohiro Kusumi wrote:
> If you are to redirect the hammer show output to a file, it's better to
> write to a file on different filesystem (e.g. ufs or another hammer).
> It's possible that hammer show never ends because what hammer show does is
> run through all ondisk btree nodes. Writing a file is adding nodes into the
> btree of that filesystem.
> 2016-01-23 0:44 GMT+09:00 Tomohiro Kusumi <kusumi.tomohiro at gmail.com>:
>> (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?


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