Okay, we tried the easy way and Steam seems to be a pain in the ass, especially when it comes to Arma 3 mod files.
So now here's a procedure to move all of the Arma 3 steam mods to another location, by messing with the Windows filesystem underneath Steam. This is not for the faint of heart, and may result in needing to download all your mods anyway. Ensure your new partition is set up and has PLENTY of free disk space. Good luck!
- Find the Arma 3 game folder -
- Open the Steam Client
- Open the LIBRARY tab
- Find Arma 3 in the list, right click and select Properties
- Select the LOCAL FILES tab and click the BROWSE LOCAL FILES... button
- in a default install this should be similar to C:\Program Files (x86)\Steam\steamapps\common\Arma 3
- Close Steam, close Arma 3 and close anything else that might have these files in use.
- Open a command prompt with Administrator rights
- You can either use the Start menu, and select Run, or use the Windows key + R
- Type CMD in the run dialog
- Press Ctrl+Shift+Enter to launch CMD as an Administrator, rather than just a normal user command prompt
- the title bar of the command Window should say Administrator: C:\Windows\system32\cmd.exe
Be careful in this window - commands typed in here can Do Stuff and Break Stuff !
- Change to the Steam workshop folder:
- cd C:\Program Files (x86)\Steam\steamapps\workshop\content
- Move the existing mod folder for Arma 3 to another name:
- move 107410 107410-old
- Create a 'symbolic' link pointing to a new location on your new partition:
- mklink /d 107410 D:\Arma-107410
- Move the actual files from the backup area to the new location
- move 107410-old\* D:\Arma-107410\
- You're done!
Reminder: If you have spaces in any of your folder names, you will need to use "quotes" around them in any of the commands above.
Depending on how many mods you downloaded for Arma 3, you should now have more disk space on your C: drive.
(continue reading only if you're curious why Steam has no idea about mod files)
Steam has no idea how big the Arma 3 mod files are, because of the following:
Directory of C:\Program Files (x86)\Steam\steamapps\common\Arma 3\!Workshop 09/02/2019 09:50 AM <DIR> !DO_NOT_CHANGE_FILES_IN_THESE_FOLDERS 13/02/2019 09:18 AM <JUNCTION> @@Air Cav Vietnam [\??\C:\Program Files (x86)\Steam\steamapps\workshop\content\107410\1171816640] 11/02/2019 10:15 PM <JUNCTION> @3CB BAF Equipment [\??\C:\Program Files (x86)\Steam\steamapps\workshop\content\107410\893328083] 11/02/2019 10:25 PM <JUNCTION> @3CB BAF Units [\??\C:\Program Files (x86)\Steam\steamapps\workshop\content\107410\893346105] 11/02/2019 10:34 PM <JUNCTION> @3CB BAF Vehicles [\??\C:\Program Files (x86)\Steam\steamapps\workshop\content\107410\893349825] 11/02/2019 10:25 PM <JUNCTION> @3CB BAF Weapons [\??\C:\Program Files (x86)\Steam\steamapps\workshop\content\107410\893339590] 09/02/2019 02:15 PM <JUNCTION> @3den Enhanced [\??\C:\Program Files (x86)\Steam\steamapps\workshop\content\107410\623475643] 12/02/2019 12:49 AM <JUNCTION> @7Y Assets WW2 [\??\C:\Program Files (x86)\Steam\steamapps\workshop\content\107410\1202636528] 09/02/2019 10:02 AM <JUNCTION> @ace [\??\C:\Program Files (x86)\Steam\steamapps\workshop\content\107410\463939057] 09/02/2019 04:58 PM <JUNCTION> @Achilles [\??\C:\Program Files (x86)\Steam\steamapps\workshop\content\107410\723217262] 13/02/2019 08:32 AM <JUNCTION> @Advanced Rappelling [\??\C:\Program Files (x86)\Steam\steamapps\workshop\content\107410\713709341] 11/02/2019 11:14 PM <JUNCTION> @Aliabad Region [\??\C:\Program Files (x86)\Steam\steamapps\workshop\content\107410\918639806] 09/02/2019 02:15 PM <JUNCTION> @ALiVE [\??\C:\Program Files (x86)\Steam\steamapps\workshop\content\107410\620260972] 16/04/2019 08:42 PM <JUNCTION> @AUSSOF_LITE_mas [\??\C:\Program Files (x86)\Steam\steamapps\workshop\content\107410\1655157508] 09/02/2019 10:01 AM <JUNCTION> @BG21 Slaughter Assets [\??\C:\Program Files (x86)\Steam\steamapps\workshop\content\107410\448333775] 26/03/2019 03:08 PM <JUNCTION> @BloodLust [\??\C:\Program Files (x86)\Steam\steamapps\workshop\content\107410\667953829] 09/02/2019 10:01 AM <JUNCTION> @CBA_A3 [\??\C:\Program Files (x86)\Steam\steamapps\workshop\content\107410\450814997] (...list continues for many pages)
Each mod's folder in the Arma 3 area is a junction - similar to the symbolic link we just created - only these are pointing back to the .../steamapps/workshop/ area. Technically there are no mod files under the Arma 3 folder... just links.
Hope that helps explain things.