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0 pointsnh219h ago0 comments

> fsync doesn’t just sync the file’s data, it syncs every piece of metadata the file depends on: ... directory entry

Famously not, as the man page says.

It is also said later in the article:

> POSIX strictly requires a parent-directory fsync to make a newly created file’s existence durable.

So I'm not sure why the dirent sync is claimed earlier.

0 comments

Thanks for pointing it out the mistakes. We should make it clearer, when fsync an opened file descriptor, it would only sync its own metadata. To make it truly persistent, we need to issue another fsync for the directory fd, which would make it more expensive.

dezgeg16h ago

You don't need to do that for every write though. Only when the database file is created.

thomas_fa16h ago

Yes, especially for our object storage each putObject would need to create new entry for in the (data)name space which would need fsync for dir fd.

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