Hi Ravi,
The storage system cannot perform properly when the root volume vol0 is full.
It usually fils up because of log files, forgotten core files (from a system panic) or packet traces. Here is a document about this in the Library:
https://library.netapp.com/ecmdocs/ECMP1196798/html/GUID-F937AFE5-197D-4C12-A0D6-628276D5C6D9.html
The best practice is never to use the root volume to store data and to regularly clean up these kinds of files. For the log files, there is usually a cron script which deletes old log files.
Hope this helps,
Florian