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"Do copy acceleration utilities actually lower file transfer speeds?"

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paulobrabo:
Hey guys, long time no talk, but lurking daily.

I'd love to hear your take on this: Samer from freewaregenius concludes that copy acceleration utilities on Windows make things actually worse:

http://www.freewaregenius.com/do-copy-acceleration-utilities-actually-lower-file-transfer-speeds-our-tests-say-yes/



What now? Do copy acceleration software works? From a technical standpoint, can it work?

mouser:
Excellent report by Samer.

However, I will echo what some of the commenters on the post have said, which is that when I have used suched utilities such as SuperCopier and Terracopy, it's not because I wanted to speed up the absolute transfer time for copying a large number of files, it's because they are much more robust and flexible -- and fail much more gracefully -- wheras default windows copy will completely abort and die midway if a single file copy out of a thousand fails.

Renegade:
Interesting... I would like to know HOW those utilities are doing it. Are they using a Windows API? Or have they written their own drivers?

f0dder:
Interesting... I would like to know HOW those utilities are doing it. Are they using a Windows API? Or have they written their own drivers?-Renegade (August 10, 2012, 06:33 AM)
--- End quote ---
Obviously using APIs, you'd have to be insane involving drivers in this.

But even at the API level, there's a ton of ways to go about it...

memory mapped files.
normal I/O, buffered vs. unbuffered, and chunksize.
async I/O, possibly using I/O Completion Ports (IOCP would be insane overkill for filecopy, but hey).

Also, a lot of stuff happened from XP to Vista. Pre-Vista, the maximum transfer size you'd get (can't remember if this was all the way down at DMA level, or "just" some kernel<>usermode thing) was 64kb. For Vista/Win2k8 this was increased to (iirc) 4MB for desktop versions and 64MB for server versions.

40hz:
+1 with Mouser and some of the comments on the original article. I was only in the habit of using TeraCopy for it's error reporting and the ability to continue after it encountered a bad file. However, TeraCopy did seem to speed up massive transfers to and from networked drives. But I never did any serious testing on that so it may have only seemed faster to me.

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