![]() ![]() The remaining six represent the Scsi ids of the fibre channel attached LUNs. The two initial Scsi ids represent the local disks (/dev/sda and /dev/sdb). Using the command scsi_id for each /block/a-h (for example, for /dev/sda we type scsi_id -g -s /block/sda) generates the output: Typing fdisk -l yields (output edited for clarity): The SAN connection on the server is handled by the Redundant Disk Array Controller (RDAC) muti-path proxy driver (mpp). Our sample system consists of a x86_64 server running Red Hat Enterprise Linux 5.5 with two local disks and six remote disks that reside on a SAN connected to the server through a fibre channel HBA. For such reasons, identifying the mapping of the LUNs to the fdisk list is of importance. A LUN may have special characteristics such as a wide RAID-stripe or cache setting that a file system like General Parallel File System (GPFS) relies on to optimize performance. For example, one or more of the disks composing a LUN may be failing and user files need to be migrated off it. It is often necessary for system administrative purposes to generate this mapping. When multiple LUNs from a SAN are attached to a server the mapping to the device list generated by the fdisk command is not readily apparent. The command fdisk -l lists attached Scsi disk devices, including those from a SAN. Disk arrays that are grouped together as logical unit number (LUN) storage in SANs can also present themselves as Scsi devices on Linux servers. through a common interface to Linux-based servers. The small computer storage interface (Scsi) commonly connects hard disks, tape devices, DVD-players, floppy drives, etc. If the disks are attached via SAN, the path and port information is also extracted. The accessible disks may be installed directly on the server or connected via a host bus adapter card (HBA) to a storage area network (SAN) or switch. ![]() This note presents a technique to extract the unique Scsi id for each disk attached to a Linux-based server. Extracting WWN IDs and HBA Port Mappings from SCSI Disks under Linux
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