> Don't get too excited -- the transactions probably aren't done yet. Without > those, no filesystem that claims to journal data is really any better than a > filesystem which only journals metadata. Even once > they are implemented (or even if they are already), applications have to > support them directly.
Actually, I think transactions in a filesystem context are a bit different from the transactions you know form databases. Generally speaking, a transaction denotes a transition from one valid state to another. This transition should either be performed completely or -- in case of errors -- performed not at all (a.k.a. "roll back"). Databases allow application defined transactions (i.e. the application specifies when a valid state is being left and when one is reached again). IMHO for filesystems a transaction denotes the flushing of write buffers. "metadata only" transactions/journaling mean that even after a crash the file itself will be readable (and not pointing to e.g. sector -4711 ...). "data _and_ metadata" now means that the filesystem does also guarantee that the data itself is written completely. Please correct my if I got this totally wrong. -Andreas
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