Does compressing all files on a 50% full disk partition slow down performance?

Question

Windows Vista SP2, (uncompressed 100 GB Drive C is 50% full and Windows file indexing is on):

Drive C, where all the program files, \Windows folder and all my data is located is half full, enjoys fast disk access. I also have disk caching optimization turned on. If I were to compress all the files on drive C, would disk access be faster?.. At what point (% full) should I consider compressing drive C?.. Should I only compress the data or all the files on this drive?

Answer 1

You are assuming for there to be a relation between how full your disk is and compressing at such point, in essence it is not going to matter how full your disk is as compressing will have the same effect when you have barely any files or a ton of files. What does have an effect though is data being further from the center of your disk as well as fragmentation, which both come as you get a fuller disk (and only on a HDD it might matter). Both are, however, not problems you can't fix.

So, this in essence turns your question in "does compressing slow down disk performance?"

For this question, we already have some Q&A but they are in essence subjective:

• Compressing a slow drive for performance?

• Does compressing files in XP slow things down?

If you really want to know, measuring the performance difference will tell you whether it helps.