Re: Please Explain the Speed Difference here.

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"Tommy" <bad@xxxxxxxxxxxxx> wrote in message
news:OrUhyUGWJHA.5496@xxxxxxxxxxxxxxxxxxxxxxx
Tommy wrote:
Here is what I see for a copy test of 25 files, 1/2 of them are 500 megs
each

Delete Before Copy: ~11 secs
Delete After Copy : ~3 secs
No Delete : ~8 secs

What am I missing here?

This is so odd. It is like the delete after the copy:

CopyFile(src, tar, false)
DeleteFile(tar)

This is so funny!... (not you) because I *just now* had a long long angry
discussion with a friend about how retarded Windows is with respect to
"delete" which takes FOREVER! I suggested to my friend the following new
rule "Use copy/rename instead *to delete files fast!*".

I think the reason is (probably anyway) delete means "unlink" file from the
file system. So that means a rather lengthy wait for the process of
unlinking/rebalancing etc... to complete before you're allowed to add a new
node to the tree. If you're overwriting a file then the file system (the
tree) remains the same so it's just a matter of dumping some bytes at a
specified "location" (node).

If you try Copy/Delete/Copy I'm sure you'll find the bottleneck is in the
unlinking segment (which can occur "lazily" as the last operation - ie.
unless you want to add a new node to the tree). I don't know why "no delete"
was 8ms... how many experiments did you run? Were they randomized path
names? etc etc...

It's kind of like guaging the speed of a CPU. There's no real speed, it
depends too much on the context of what's being executed.

- Alan Carre



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