If you add more disks to the SAN, use the following procedure to scan the devices and make them available without rebooting the system:
On the storage subsystem, use the vendor’s tools to allocate the devices and update its access control settings to allow the Linux system access to the new storage. Refer to the vendor's documentation for details.
On the Linux system, use the HBA driver commands to scan the SAN to discover the new devices. The exact commands depend on the driver.
For example, for a QLogic 2300 HBA, the command is
echo scsi-qlascan >/proc/scsi/qla2xxx/<host number>
At this point, the newly added device is not known to the higher layers of the Linux kernel's SCSI subsystem and is not yet usable.
Scan all targets for a host to make its new device known to the middle layer of the Linux kernel's SCSI subsystem. At a terminal console prompt, enter
echo "- - -" >/sys/class/scsi_host/host<hostnumber>/scan
If the devices have multiple paths, run the Multipath tool to recognize the devices for Device Mapper Multipath I/O (DM-MPIO) configuration. At a terminal console prompt, enter