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How much space will be required to keep a backup of 500 GB of data.

Is there any standard way to find an answer for this question?

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closed as not a real question by Xavierjazz, random Jun 6 '12 at 1:07

It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center.If this question can be reworded to fit the rules in the help center, please edit the question.

    
at least 500GB?! (by copy 1:1 without compression) –  JohannesM May 30 '12 at 10:41
    
erm, to backup 500gb, you will need 500gb. That's just maths isn't it...?!?? –  Shevek May 30 '12 at 10:42
    
get 750GB or 1T because you don't want to just have exactly 500:500 –  Ali May 30 '12 at 11:11

2 Answers 2

up vote 6 down vote accepted

An uncompressed backup of 500 GB will take 500 GB (± file system differences).

A compressed backup will take less. How much, you ask? This depends on the compressibility of the files contained. If these are movies or images, they are already compressed. Most text files on the other hand are not.

To demonstrate how much the compression ratio can vary, here are two samples:

  • Easily compressible 100M file

    $ ls -l easy 
    -rw-r--r-- 1 me me 104857600 May 30 13:02 easy
    $ bzip2 easy 
    $ ls -l easy*
    -rw-r--r-- 1 me me 113 May 30 13:02 easy.bz2
    

    Compresses to 113 bytes.

  • Hard to compresse 113 byte file

    $ ls -l hard 
    -rw-r--r-- 1 me me 113 May 30 13:02 hard
    $ bzip2 hard 
    $ ls -l hard*
    -rw-r--r-- 1 me me 148 May 30 13:02 hard.bz2
    

    "Compresses" to a file larger than it was originally.

The only way to find out how large a compressed backup will be is to actually create it.

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If you mean compressing the data, according to type of data and how much space is used in your hard it depends. For example if you have text, it will be compressed very good. Try using "Norton Ghost".

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