Hi, maybe you ran into problems with disk space on your partitions:

Sample errors:
Filesystem Warning: Filesystem / (/dev/sda1) on *** is using 91%
"no space on / " .../dev/md2 @ 100%...
and similar

FIXING, Discovering large files

This linux command (CLI, SSH) shows 15 largest files on server in "/". Sort them recursivelly and sort them according to size. Source of this command here. Thanks to this, you can discover largest files.
du -a / | sort -n -r | head -n 15

This one is also good, shows largest directories:
find . -type d -print0 | xargs -0 du -s | sort -n | tail -10 | cut -f2 | xargs -I{} du -sh {}
from the folder you are in. source of this command: here

This will tell you partitions disk space usage
df -h