Should disk write cache be disabled for any journalised filesystem?

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Dear Jari,

In your README you write so:



2.2. Use of journaling file systems on loop device
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
... Device backed loop device can be used with journaling file systems
as device backed loops guarantee that writes reach disk platters in
order required by journaling file system (write caching must be disabled
on the disk drive, of course).
----------------------------


To my understanding, the danger is that the filesystem terminates an
operation and updates the journal. The harddisk write cache somehow
manage to write the updated journal info, but when about to write the
filedata themselves, power is lost.

Wouldn't that be a general problem with any journalised filesystem? If
so, as most OS'es nowadays have journalised filesystems, does the modern
harddisks have ways to prevent such problems, or does the harddisk
(filesystem?) driver implement some 'sync'-function before commiting the
journal?



On another topic: shouldn't the KEYSCRUB option be enabled by default?

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