JLS2009: A Btrfs update
Posted Oct 29, 2009 18:26 UTC (Thu) by Yorick
Parent article: JLS2009: A Btrfs update
Fast fsync() is of course welcome, but only really needed by some applications. The ability to guarantee that a change has been committed to permanent storage (before replying to a network request, say) is nice, but even when optimised in the way the article suggests, likely to be unnecessarily expensive when such a guarantee isn't required.
Being able to specify dependencies between different changes - don't write this to disk until that change has been committed - would make more in many cases.sense to an application that want to avoid scrambling the user's files but doesn't really care whether a particular update has taken place or not if the system crashes. A barrier would do; full transactions would be wonderful. Nothing really needs to be written to disk as long as the change is eventually done in good order.
Of course we want fast fsync() as well for those servers that are required to send us promises that they've taken care of our data, but far from all applications are like that.
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