The scsi_reserve service allows you to use SCSI reservations as a fence method. An SCSI reservation restricts access to a device such that only registered nodes can access it. During system startup, the scsi_reserve script performs this registration using a unique key, based on the node’s IP address. Once the node is registered, the script will attempt to create a reservation. There will be only one reservation per SCSI device but multiple registrants can exist for an SCSI device. Each node that will perform I/O operations to the SCSI device must then register.
The reservation informs the device how the registrants are allowed to access the device. When the cluster fences a node, the node first gets unregistered. Should the node happens to be the reservation holder then the script does nothing because there may be other nodes using the device.
The scsi_reserve service is included in the cman RPM package. To manage the scsi_reserve service for future system shutdowns and reboots, use the chkconfig tool:
# chkconfig scsi_reserve on
When enabled, the scsi_reserve script handles creation of registrations and reservations at system startup.
# scsi_reserve start
Running the scsi_reserve init script with the ‘start’ option will proceed to create registrations on all devices that were previously discovered and if necessary, it will also create the reservation.
# scsi_reserve stop
Running the scsi_reserve init script with the ‘stop’ option will attempt to remove the node’s registration key from all devices that it registered with at startup.
# scsi_reserve status
Running the scsi_reserve init script with the ‘status’ option will list the devices that the node is registered with.
The script does source the /etc/sysconfig/scsi_reserve configuration file, should it exist, but at present its contents are not used.