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How OS X Copies/Moves files?


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How OS X Copies/Moves files?
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james_p
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Join Date: Apr 2005
 
2005-09-20, 18:39

As someone who has recently made the switch to Apple. I've noticed that the speed in which files are copied or moved from one drive to another, lets say for example I am copying about 200MB of data from my laptops hard drive to an external USB 2.0 drive. This process takes slightly longer on my MAC then it does on my Windows XP machine.

Now, my theory (and I am attempting to learn here) is that the way OS X keeps files organized as they are being written to a drive is done so as to optimize their location for future reference?

Whereas my Windows machine just throws data anywhere it pleases, thus you have to defrag a drive very often.

Does that sound about right? Just trying to see if my observations are close to being correct?
Thanks

James
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Kickaha
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Join Date: May 2004
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2005-09-20, 18:42

Somewhat.

It's true that the filesystem on MacOS X (HFS+) does do some defragging on the fly. Files under 20MB, when they're written, get put in a new contiguous block if at all possible. (If it's not possible, you've got problems already.)

A straight copy though, to a fresh drive, *should* be fairly contiguous to begin with, but if it's a drive that's already got stuff on it, then yes, your guess is probably correct.

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naren
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2005-09-20, 20:37

In general, OS X is slower transferring files using USB 2.0 than WinXP. I have no idea why. I believe Ars Technica did a piece on this a while ago.

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torifile
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Join Date: May 2004
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2005-09-20, 20:44

Now that autocorrect is off, the burden is on us asses. It's Mac, not MAC.
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julesstoop
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Join Date: Oct 2004
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2005-09-21, 01:11

On a related note. I've noticed that it sometimes takes a very long time to copy an application (package containing maybe several thousands of seperate files) from say a mounted .dmg to my preferred location on my HD. I have had this take more than 5 minutes with something like a 20 MB app (!).
They only thing I can think of is that spotlight is indexing all of the contents. So maybe in your case the spotlight indexing is also one of the culprits.

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james_p
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Join Date: Apr 2005
 
2005-09-21, 08:02

Yep, I think a combination of Spotlight (in some instances) with maybe some additional File System work going on behind the scenes would account for the delay at times.

Thanks for the feedback all.
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Dave
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Join Date: May 2004
Location: Bay Area, CA
 
2005-09-21, 14:11

Quote:
Originally Posted by julesstoop
On a related note. I've noticed that it sometimes takes a very long time to copy an application (package containing maybe several thousands of seperate files) from say a mounted .dmg to my preferred location on my HD. I have had this take more than 5 minutes with something like a 20 MB app (!).
There's an overhead associated with creating files. Writing 200 1MB files takes longer than 1 200MB file. I have no idea what the overhead is though, so I can't say of the "several thousands of separate files" is why it took so long.

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julesstoop
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Join Date: Oct 2004
Location: Leiden, the Netherlands
 
2005-09-21, 14:53

I know, maybe it was more like one thousand seperate filesystem entries (which hints to an answer by itsself)
Still, the overhead seems to have gotten a lot larger since 10.4. Something I've typically come to associate with Spotlight.

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