Robert Milkowski wrote:
Hello Eric,
Monday, August 7, 2006, 6:29:45 PM, you wrote:
ES> Robert -
ES> This isn't surprising (either the switch or the results). Our long term
ES> fix for tweaking this knob is:
ES> 6280630 zil synchronicity
ES> Which would add 'zfs set sync' as a per-dataset option. A cut from the
ES> comments (which aren't visible on opensolaris):
ES> sync={deferred,standard,forced}
ES> Controls synchronous semantics for the dataset.
ES>
ES> When set to 'standard' (the default), synchronous
ES> operations such as fsync(3C) behave precisely as defined
ES> in fcntl.h(3HEAD).
ES> When set to 'deferred', requests for synchronous
ES> semantics are ignored. However, ZFS still guarantees
ES> that ordering is preserved -- that is, consecutive
ES> operations reach stable storage in order. (If a thread
ES> performs operation A followed by operation B, then the
ES> moment that B reaches stable storage, A is guaranteed to
ES> be on stable storage as well.) ZFS also guarantees that
ES> all operations will be scheduled for write to stable
ES> storage within a few seconds, so that an unexpected
ES> power loss only takes the last few seconds of change
ES> with it.
ES> When set to 'forced', all operations become synchronous.
ES> No operation will return until all previous operations
ES> have been committed to stable storage. This option can
ES> be useful if an application is found to depend on
ES> synchronous semantics without actually requesting them;
ES> otherwise, it will just make everything slow, and is not
ES> recommended.
ES> There was a thread describing the usefulness of this (for builds where
ES> all-or-nothing over a long period of time), but I can't find it.
I remember the thread. Do you know if anyone is currently working on
it and when is it expected to be integrated into snv?
I'm slated to work on it after I finish up some other ZIL bugs and performance
fixes.
Neil
_______________________________________________
zfs-discuss mailing list
zfs-discuss@opensolaris.org
http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
