I copied a lot of files in my mounted Windows drive from Ubuntu and I subsequently ran into Error opening file '/media/windows/<some-file-path>': No space left on device error. I checked the output of df -i command to see if I had ran out of inodes for the mounted Windows drive:

Filesystem        Inodes   IUsed     IFree IUse% Mounted on
/dev/sda5        2363904  504119   1859785   22% /
udev              207621     522    207099    1% /dev
tmpfs             211487     450    211037    1% /run
none              211487       3    211484    1% /run/lock
none              211487       7    211480    1% /run/shm
none              211487      19    211468    1% /run/user
/dev/sda2      458686680 2588876 456097804    1% /media/windows

As above output shows, lots of inodes are available for /media/windows drive.

I have plenty of disk space left - around 500GB. What's the problem then?