I have posted a very similar question here before.

A similar thing happened this morning. I received a Low Disk Space warning

The volume "InternalHDD" has only 873.8 MB disk space remaining

I clicked the button "Examine...", and up comes Disk Usage Analyzer which (unfortunately) says

Could not scan folder "/mnt/InternalHDD" or some of the folders it contains

So I start the Disks utility to have a look, and the Disks utility reports that my disk "InternalHDD" has 52 GB free.

There's no immediate problem, because I was able to free up 256GB immediately on my "InternalHDD".

What I want to know is:

  • Why does this happen?
  • What is being measured to give the 873.8 MB free disk space number?
  • What is being measured to give the 52 GB free disk space number?
  • Why are these numbers different, when they are supposedly for the exact same disk at the same moment?

Here are screenshots of each of these:

marked as duplicate by psusi, Fabby, Volker Siegel, David Foerster, Elder Geek Mar 4 '15 at 17:49

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

  • If it's not a duplicate, write a comment @Fabby... – Fabby Dec 7 '14 at 20:25
  • I just had a look at [What is taking up so much space on my disk, beside the filesystem?][1] and it is different to my post. That post is described well by the post title, but my post is because I don't know how much space is left on my disk, because I am given two completely different numbers. [1]:askubuntu.com/questions/17467/… – el_gallo_azul Dec 7 '14 at 22:32
  • 5% of storage is reserved for root as I recall. This may be the source of the discrepancy you are seeing. – Elder Geek Dec 18 '14 at 16:48
  • OK thanks. That made sense at first, but then I realised that what you say would (as far as I can tell) only affect the disk containing root, which in my case is an SSD, whereas my "InternalHDD" is a second drive within the same case which I use for things requiring zillions of write cycles. – el_gallo_azul Dec 19 '14 at 3:43
  • The 5% reserve does not only affect the root. – psusi Dec 22 '14 at 21:50