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When we used redundant SAN Switch to present the same LUN, Linux will recognize 1 LUN become 2. In the example we can see the size of /dev/sdb as same as /dev/sde (8069.5 GB) and /dev/sdc as same as /dev/sdd (5763.9 GB), actually we only created 2 LUN in the storage:

# fdisk -l

Disk /dev/sdb: 8069.5 GB, 8069496176640 bytes
255 heads, 63 sectors/track, 981060 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

Disk /dev/sdb doesn't contain a valid partition table

Disk /dev/sdc: 5763.9 GB, 5763927244800 bytes
255 heads, 63 sectors/track, 700757 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

Disk /dev/sdc doesn't contain a valid partition table

Disk /dev/sdd: 8069.5 GB, 8069496176640 bytes
255 heads, 63 sectors/track, 981060 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

Disk /dev/sdd doesn't contain a valid partition table

Disk /dev/sde: 5763.9 GB, 5763927244800 bytes
255 heads, 63 sectors/track, 700757 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000 

To unity the different path, we can used “multipath”‘

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