Does copying files to Dropbox folder increase disk space used?

[jhedleyj]

I copied about 40Gb of files to the Dropbox folder which duly uploaded to Dropbox as expected.  So far so good. However, when I checked my disk space usage on Macintosh HD "Get info" nothing had changed. I expected it to increase by 40Gb. I am led to believe that by copying files to Dropbox then I would be duplicating them and should expect my disk usage to increase accordingly. I do not have Smart Sync connected. My intention is to copy my data to Dropbox and it to be stored as a backup (and occasional sharing).

Could any one offer any explanation for this behaviour?

[Lusil]

Hey @jhedleyj, welcome to the Dropbox Community!

You're right, if you add 40 GB of content and they are synced as local, then you should see an increase of 40 GB on your Dropbox account and your hard drive. 

To make sure we're on the right path, could you please hover over your Dropbox icon on your menu bar and let me know what it shows?

Keep me posted!

[jhedleyj]

If you mean the desktop app the answer is "nothing" and the same for the web page. I am running OSX Catalina and my disk is formatted as APFS if that helps.

[Lusil]

Thanks for getting back to me, @jhedleyj. 

If you don't see the Dropbox icon next to your computer's clock, it means that the desktop app isn't running and you'll have to relaunch it from your applications menu. 

Also, could you let me know a couple more details:

• Do you see the original folders/files in the location which you copied them from?
• How large is the content in the original path and the ones in your Dropbox folder?

Let me know what you find!

[jhedleyj]

Hello again, Lusil

The apps are now running perfectly. I have the Smart Sync setting for all folders as Local (not Online). 

I have a 1Tb HD on my iMac. Get info shows it has 721Gb free with 286 Gb used which will include the 231 Gb of data for 24008 files that I have loaded into Dropbox. This makes sense to me.

However, I have copied the same folders and the data into the Dropbox folder (showing exactly the same figures i.e., 231Gb data for 24008 files).

It is a long time since I went to primary school but 1024Gb - 231Gb - 286Gb does not equal 720!

I am very very puzzled by this as, as far as I am concerned, I have made an identical copy of 231Gb of data on the very same hard disk (or have I?) but it is not being accounted for.

Regards

[IanDavidCottam]

Either 

1) You moved the files and folders, rather than copied them (but you seem confident that this is not the case; so:

2) You are seeing APFS's optimisation which enables very fast copies by just copying the metadata of the files and folders. This is sometimes called copy-on-write; i.e. more file storage will only be taken up if the original or the copy is changed in some way.

[jhedleyj]

I definitely copied them.

So, if I understand it correctly, after "copying", the files remain in the same place on the disk and are referenced to both Dropbox and their original location but are not duplicated as I originally thought. Thus if I alter a file in some way APFS saves the amended version as a new file thereby occupying more disk space. That would appear to make sense.

Am I correct?

Sounds very Schrodinger-ish!

Many thanks for your help.

[IanDavidCottam · Accepted solution]

Yes, essentially, you are correct.

It is a neat (time/space) optimisation that can be confusing at times.