Comment # 29 on bug 1017461 from Jan Ritzerfeld

> [...] 
> Can I disable quotas? I'm not sure whether this will harm snapper.

It actually will if you used quotas before:
# snapper cleanup number
quota not working (preparing quota failed)

# snapper get-config | grep QGROUP
QGROUP                  | 1/0

This fixes it:
# snapper set-config QGROUP=

However, I do not know to renable it! Maybe you need the original value of
QGROUP.