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How does copying files work with regards to RAM, and can I speed this up?

When I copy a file from my PC to an external hard drive, is it copied in RAM first and then start transferring the data? How does it work if the file is bigger than RAM? If it is a video file.

Also, how different it is if I am copying the file from one folder to a different folder in my PC.

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marked as duplicate by Karan, Andrew Lambert, Mike Fitzpatrick, 8088, sawdust Nov 28 '12 at 1:21

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It depends on your system and file system. –  Cole Johnson Nov 27 '12 at 23:38
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Copying a file is typically done by reading a chunk into memory (RAM), writing it to the destination, and repeating until end-of-file is reached.  Chunk size may be 512 bytes or a small multiple thereof (e.g., 4096); some copy programs (notably, Unix’s dd) let you specify the size.  It shouldn’t matter whether the source and destination are in the same folder or on totally different media.

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But copying files from one folder to other in same PC is much faster than copying to an external drive. Do you also mean size of RAM doesnt make any difference? –  vkv Nov 27 '12 at 23:44
    
it is because if the external drive is USB 2, you'll get around 30MB/s of actual speed to the drive. A regular desktop HDD will be closer to 100MB/s –  Justin Nov 28 '12 at 0:17
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