There is some issues with the hard disk file system memory space. I would suggest you to do the following:
1) Issue a check disk from the debug promt.
NS_CSS_MASTER(debug)# chkdsk ?
Execute command
no-fix Perform checking without fixing errors
quick
NS_CSS_MASTER(debug)# chkdsk -----------> press enter.
Verifying Clusters(-) 11747
Then check if the issue persists. If yes then go to the second step.
2) Reboot the CSS and check if the issue persists.