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On 26/09/11 22:29, David Magda wrote:
> Talking about "7.55 GB" is mostly useless as well. If it's a dozen
> video files then stat()ing them all with be done very quickly by
> just running find(1). If however the 7.55 GB is made up of
> 7,550,000 files then going through them would take quite a long
> time.

Point taken, although "zfs diff" time is (should) proportional to
changes, not to number of files.

> How long would it take for (say) rsync to walk two file systems
> (or snapshot directories) to come up with the same list?  Ten
> minutes may seem like a lot in 'absolute' terms, but if something
> like rsync takes an hour or two to stat() every file, then it's a
> big improvement.

"rsync" takes a bit less than 7 minutes. So "zfs diff" is actually
slower!.

> So the question is: by what metric are you comparing that you came
> up with the "disappointing" conclusion? Why is ten minutes
> disappointing? What would /not/ be disappointing to you? 8m? 5m?
> 3.14 seconds?

If I change 10 files in dataset with a trillion files, I would expect
less than a couple of seconds. Given the tree walking pruning with
"birthdate" age, I actually think this is reasonable (you skip over
entire on-disk branches if there are no changes under them).

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