Personally I don't remember seeing this message before, but looking up in the EMS catalog, there is an entry for this error. I suggest raise a call or raise a ticket plz, just to be on the safer side ASAP.
EMS Identifier: bootfs.varfs.issue Deprecated: Deprecated as of version 9.0 to rename the event to boot.varfs.backup.issue. Severity : ERROR Description This message occurs when an error is detected while trying to backup the var filesystem to the boot media or mroot file system. Corrective Action : Contact NetApp technical support. Syslog Message The var filesystem backup failed (%s) Parameters err_str (STRING): Error string.
In the mean time, while you log a call: check mroot volume space on the root aggregate.