[Lustre-discuss] filesystem corruption

[Richard Smith]

Peter Kjellstrom wrote:
> I also feel that "lie" is a bit incorrect as a description. However, 
> while FUA
> does exist it's typically ignored by controllers. If you're lucky you 
> have
> a "ignore FUA: enable/disable" setting.

This is a concern, that FUA might be ignored silently. I wasn't aware that
implementing FUA was optional. If it is optional, then I would have expected
a mode page to describe whether a given device implements it. Sounds like
it would be safer to use SYNCHRONIZE CACHE unless devices lie about that 
too.
I realise that synchronisation isn't by itself sufficient to avoid 
corruption:
there is still a need to use techniques, such as a journal, to provide the
atomic update semantics required when a change involves multiple 
non-contiguous
blocks.

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