Re: Linux 2.6.29
From: Bill Davidsen
Date: Mon Mar 30 2009 - 15:03:22 EST
Andreas T.Auer wrote:
On 30.03.2009 02:39 Theodore Tso wrote:
All I can do is apologize to all other filesystem developers profusely
for ext3's data=ordered semantics; at this point, I very much regret
that we made data=ordered the default for ext3. But the application
writers vastly outnumber us, and realistically we're not going to be
able to easily roll back eight years of application writers being
trained that fsync() is not necessary, and actually is detrimental for
ext3.
And still I don't know any reason, why it makes sense to write the
metadata to non-existing data immediately instead of delaying that, too.
Here I have the same question, I don't expect or demand that anything be done in
a particular order unless I force it so, and I expect there to be some corner
case where the data is written and the metadata doesn't reflect that in the
event of a failure, but I can't see that it ever a good idea to have the
metadata reflect the future and describe what things will look like if
everything goes as planned. I have had enough of that BS from financial planners
and politicians, metadata shouldn't try to predict the future just to save a ms
here or there. It's also necessary to have the metadata match reality after
fsync(), of course, or even the well behaved applications mentioned in this
thread haven't a hope of staying consistent.
Feel free to clarify why clairvoyant metadata is ever a good thing...
--
Bill Davidsen <davidsen@xxxxxxx>
"We have more to fear from the bungling of the incompetent than from
the machinations of the wicked." - from Slashdot
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