[All Linux Operating Systems] The multipath command will issue an error indicating that too many files are open when the number of open files exceeds the configured host system limit.
# lsof | wc -l
# ulimit
If necessary, increase the system limit by following the instructions in the operating system documentation. In addition, set the max_fds value in the /etc/multipath.conf file to an appropriate limit.
Some operating systems may require a host reboot is required to ensure that the system limits are updated.