IBM LUNs on Linux - David Woodsmall

8/03/2019 - Optimized for Firefox 68.0.1

COPYRIGHT 2005 thru 2019 - David Woodsmall



Unless told differently (there are multiple techniques), Linux assumes that your LUNs are numbered consecutively starting with LUN 0. LUNs not numbered consecutively are called Sparse LUNs. Red Hat Enterprise Linux 3 & 4 The SCSI standard requires that all SCSI devices respond to Logical Unit Number (LUN) zero. Some SCSI devices fail when they are scanned for Logical Unit Numbers (LUNs) greater than zero. Other devices require that LUNs must be numbered sequentially. The Red Hat Enterprise Linux 3 Update 1 kernel contains a list of devices that have been tested and shown to work correctly when scanned for non-zero LUNs, and non-sequential LUNs. Only devices on this list are scanned by default. This default behavior can be overridden on a system-wide basis by adding the following entry to the /etc/modules.conf (2.4 Kernel) file: options scsi_mod max_scsi_luns=255 After modifying modules.conf, it is necessary to rebuild the initial ramdisk file using the mkinitrd script. Refer to mkinitrd man page (using the command man mkinitrd) for more information about creating the initial ramdisk image. When this option is used, the LUN numbers on the device must be assigned sequentially, starting with zero. RHEL: options scsi_mod max_scsi_luns=255 "max_scsi_luns" CHANGED to "max_luns" under 2.6 kernel option: max_scsi_luns CHANGED under 2.6 kernel


fdisk - mount /dev/sda1 /fibre/disk1 type ext3 (rw) ... /dev/sdx1 /fibre/disk24 type ext3 (rw)


Use: cat /proc/mpp to see what LUNs RDAC will present to the host.

QLogic HBAs

cat /proc/scsi/qla23xxx/ (if using a qla2300 HBA card) cat /proc/scsi/qla23xxx/1

Storage Manager (SM) - IBM

Use "SMdevices" on LINUX hosts to see which drives/arrays in in owned by which controller are mapped to what /fibre/disk# Use "Manage=>Storage=>Disk Management" on WINDOWS hosts to handle mapping of Storage Manager logical disks


RHEL - Read Hat Enterprise Linux: How do I setup multiple LUNs on Red Hat Enterprise Linux 4? Why can I only see one LUN if using qlogic HBAs and the LILO bootloader, when exporting multiple LUNs from a SAN device? How can you get fdisk to see new fiber channel attached disk LUNs without rebooting? How do I enable multipathing from multiple I/O controllers back to the same storage in Red Hat Enterprise Linux 3? How do I install the iSCSI initiator for Red Hat Enterprise Linux 3 or 4? How can multiple systems access a single iSCSI LUN? How do I configure Red Hat Enterprise Linux 3 or 4 to access iSCSI storage? How do I configure iSCSI devices to be mounted at boot time? What changes do I need to perform on Red Hat Enterprise Linux on each cluster member when configuring them for clustering? I'm not having my SCSI device recognized in the Red Hat Enterprise Linux 2.4 Kernel, what can I do? Installing and Configuring Red Hat Enterprise Linux - Ref Hat Steps for Installing and Configuring the Red Hat Linux Distribution