Do file transfers damage files?

[TonyBoudro]

I was wondering if transferring a file, either online or from one hard drive to another (this also includes transfers to portable drives like USB sticks, etc.), could damage or alter the original file in any way.

Thanks in advance.

- Tony

 

[rgd1101]

Is possible, but you don't usually see it, why are you asking?

 

[Guest]

Two Words

Back Up!

 

[Paperdoc]

It is not supposed to. The whole point of digital data is that it is all exactly right, or it's wrong - there is not "slight alteration". So any copy is EXACTLY the same as the original.

BUT ... there is a small possibility that, when the copy is written, a mistake is made in one digital bit, altering the data. There are automatic behind-the-scenes data checking processes that catch and fix most such little glitches, so the ones that actually remain as real errors are rare! But it is possible - nothing is perfect.

 

[TonyBoudro]

Thanks for the replies,

The reason I'm asking is that I recently noticed one of my files has exactly one less bit than my duplicate. I'm not sure if I downloaded another version of it or if I simply used the old fashioned "Ctrl+C Ctrl+V" method to store it somewhere safe. It sounds a lot like what Paperdoc is mentioning.

Thanks again.

 

[Pinhedd]

I was wondering if transferring a file, either online or from one hard drive to another (this also includes transfers to portable drives like USB sticks, etc.), could damage or alter the original file in any way.

Thanks in advance.

- Tony

Nope, not in the slightest.

Excessive writes to the same physical location on any storage medium will wear down the medium over a long period of time. This is why rewritable CDs don't last very long. Hard drives can handle hundreds of thousands of rewrites to the same location before it becomes unusable.

Logically a copy of a file is a bit for bit copy of the original. Digital data is designed to be infinitely replicable. When there's the possibility of data degradation in transmission (such as over the internet) the transmission protocol contains a method for validating whether or not the received data contains any errors; if it does contain errors, the recipient will ask the sender to resend the data again.

On a related note, when looking at the size of a file there are two separate and related metrics. First is the actual file size which is a measure of the number of bytes between the first byte in the file and the end of the file. Second is the "size on disk" which will always be as large as or larger than the file size and will always be a multiple of the file system's allocation unit size (usually 4KiB or 4096 bytes).

 

[TonyBoudro]

Best answer selected by TonyBoudro.