I did some quick checks to investigate how size helps with deduplication.<p>Size is a fast initial differentiator because scanning for file size only needs to read metadata, but how good does it differentiate?<p><pre><code>  # all files
  find ~ -type f | wc -l
  1098045
  # files with a unique size
  find ~ -type f -printf &#x27;%s\n&#x27;|sort|uniq -c|grep &#x27; 1 &#x27;|wc -l
  48437
  # most prevalent sizes (prevalence vs size)
  find ~ -type f -printf &#x27;%s\n&#x27;|sort |uniq -c |sort -nr|head
  36972 0
  12707 24
   9480 22
   8036 39
   5025 12
   4804 26
   3879 6
   3232 76
   2946 38
   2855 20
</code></pre>
In my home dir, less than 5% of files have a unique size.