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" <mill...@openbsd.org> написа: >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
