In Linux,  the kernel can force flushing the disk cache (which also can be 
disabled )  via fsync()  call . That feature  is called  'write barrier'. As 
I'm not a developer, I never read that portion of the source of openBSD , so I 
got no idea if similar logic can be used in openBSD.

Does  'softdep'  represents  the behaviour of 'write barriers' in Linux ?

Best Regards,
Strahil Nikolov

На 13 юни 2020 г. 19:56:18 GMT+03:00, "Todd C. Miller" <> 
>On Sat, 13 Jun 2020 12:12:05 -0400, Nick Holland wrote:
>> On 2020-06-11 12:07, Strahil Nikolov wrote:
>> > I always thought that 'sync' mount option  is enough  to avoid
>> > corruption of the FS. Am I just "fooling" myself  ?
>> As "sync" is the default...yes, I think you are.
>Actually, by default only metadata is written synchronously.  The
>"sync" mount option causes data to be written synchronously too.
>Of course, the disk *itself* has a cache so even with synchronous
>writes you can't be sure the data has actually made it to the platter.
>So yes, I agree that sync mounts are not really enough to help here.
>You are probably correct that softdep is better for this kind of
>thing since it does a better job of keeping the filesystem in a
>consistent state, at the cost of missing data when there is an
>unclean shutdown.  In theory, the on-device cache can still cause
>issues when you lose power though.
> - todd

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