The corresponding log file of each Block Storage service is stored in the /var/log/cinder/ directory of the host on which each service runs.

Log files used by Block Storage services

Log file	Service/interface (for CentOS, Fedora, openSUSE, Red Hat Enterprise Linux, and SUSE Linux Enterprise)	Service/interface (for Ubuntu and Debian)
api.log	openstack-cinder-api	cinder-api
cinder-manage.log	cinder-manage	cinder-manage
scheduler.log	openstack-cinder-scheduler	cinder-scheduler
volume.log	openstack-cinder-volume	cinder-volume