If you have run out of inodes no new files can be created, this causes all sorts of issues. Generally this doesn't happen unless there is a script or something that is creating millions of files that it really shouldn't be.

To see first run: df -i

If you have used 100% of your inodes on a drive then you need to run:

find */ | sed 's!/.*!!' | uniq -c

Start at / and move your way up the folder until you determine where all the files are.

Then remove the offending files, as there is likely millions in the folder to remove them you will need to move into the folder where the files exist and type:

find . -type f -print -delete