What about other filesystems?

Posted Jul 23, 2021 17:55 UTC (Fri) by andresfreund (subscriber, #69562)
In reply to: What about other filesystems? by Wol
Parent article: Fast commits for ext4

You can trust the data if you tell the OS you want to pay the price (use fsync, or O_SYNC/O_DSYNC) and you only rely on data known to be flushed after a crash.

The alternative you're proposing basically implies that writes cannot be buffered for any meaningful amount of time. Oh, your browser updated it's history database? Let's just make that wait for all temporary files being written out, the file being copied concurrently, etc. And what's worse, do not allow any concurrent sync writes to finish (like file creation), because that would violate ordering.

Ext3's ordering guarantees were weaker and yet lead to horrible stalls all the time. There constantly were complaints about Firefox's SQLite databases stalling the system etc.

The OS/FS aren't magic.

What about other filesystems?

Posted Jul 23, 2021 18:01 UTC (Fri) by andresfreund (subscriber, #69562) [Link]

> The OS/FS aren't magic.

In particular they have no reliable way of knowing which files (or even parts of files) are related and need constrained ordering between writes, and which are unrelated and thus can handled independently.