it’s typical option for Sonexion storages.
journal checksum is enough to cover a corruptions for external journal,
but provide a less overhead than full metadata checksums.
In our’s workload - any checksums is source of huge latency, so minimal option had enabled.
from other sides it option can enabled without disk format change.
I was have plan to add v2/v3 checksums to patch series but images need to prepared for it.
In this particular usage it was used to find a bug in jbd2 code, with back porting commit
de92c8caf16ca84926fa31b7a5590c0fb9c0d5ca
jbd2: speedup jbd2_journal_get_[write|undo]_access()
to rhel7 code.
that commits introduce a race window while frozen buffer had modified in parallel thread.
this race likely to be fixed by
ee57aba159a5c329dc78c181a3ae0549e59f0925
jbd2: simplify code flow in do_get_write_access()
which described as cleanup.
> 22 нояб. 2018 г., в 3:07, Theodore Y. Ts'o <tytso@xxxxxxx> написал(а):
>
> On Mon, Nov 19, 2018 at 12:16:50PM +0300, alexey.lyashkov@xxxxxxxxx wrote:
>>
>> journal checksum v1 cover an all blocks in journal descriptor.
>> This checksum stored into commit block and check with commit
>> block reading.
>
> I'm really curious --- why do you care about journal_checksum v1 at
> all? It rarely used, and the journal_checksum v3 is much superior.
>
> - Ted
>
