Example of a SCSI disk configuration

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To see the device mapper-created device nodes of the prepared devices on the host, enter:
# multipathd -k'show topology'
36005076305ffc1ae00000000000021df dm-3 IBM     ,2107900         
size=30G features='1 queue_if_no_path' hwhandler='0' wp=rw
`-+- policy='service-time 0' prio=0 status=active
  |- 1:0:7:1088372769 sdm   8:192  active ready running
  |- 1:0:3:1088372769 sdn   8:208  active ready running
  |- 1:0:5:1088372769 sdo   8:224  active ready running
  |- 1:0:4:1088372769 sdl   8:176  active ready running
  |- 0:0:3:1088372769 sdbd  67:112 active ready running
  |- 0:0:4:1088372769 sdax  67:16  active ready running
  |- 0:0:8:1088372769 sdbj  67:208 active ready running
  `- 0:0:6:1088372769 sdbp  68:48  active ready running
...
36005076305ffc1ae00000000000021d5 dm-0 IBM     ,2107900         
size=30G features='1 queue_if_no_path' hwhandler='0' wp=rw
`-+- policy='service-time 0' prio=0 status=active
  |- 1:0:4:1087717409 sdg   8:96   active ready running
  |- 1:0:7:1087717409 sdq   65:0   active ready running
  |- 1:0:5:1087717409 sdi   8:128  active ready running
  |- 1:0:3:1087717409 sdf   8:80   active ready running
  |- 0:0:4:1087717409 sdaw  67:0   active ready running
  |- 0:0:3:1087717409 sdbc  67:96  active ready running
  |- 0:0:6:1087717409 sdbo  68:32  active ready running
  `- 0:0:8:1087717409 sdbi  67:192 active ready running
Define the devices:
<disk type="block" device="disk">
    <driver name="qemu" type="raw" cache="none" io="native" iothread="1"/>
    <source dev="/dev/mapper/36005076305ffc1ae00000000000021df"/>
    <target dev="vda" bus="virtio"/>
    <address type="ccw" cssid="0xfe" ssid="0x0" devno="0x1a10"/>
</disk>
<disk type="block" device="disk">
    <driver name="qemu" type="raw" cache="none" io="native" iothread="2"/>
    <source dev="/dev/mapper/36005076305ffc1ae00000000000021d5"/>
    <target dev="vdb" bus="virtio"/>
    <address type="ccw" cssid="0xfe" ssid="0x0" devno="0x1a12"/>
</disk>
The virtual server sees the standard device nodes, which are of the form /dev/vd<x>, where <x> represents one or more letters. The mapping between a name and a certain device is not persistent across guest reboots. To see the current mapping between the standard device nodes and the udev-created by-path device nodes, enter:
[root@guest:] # ls /dev/disk/by-path -l
total 0
lrwxrwxrwx 1 root root  9 May 17:18 ccw-0.0.1a10 -> ../../vda
lrwxrwxrwx 1 root root 10 May 14:21 ccw-0.0.1a12 -> ../../vdb
The virtual server always sees the control unit type 3832. The control unit model indicates the device type, where 02 is a block device:
[root@guest:] # lscss
Device   Subchan.  DevType CU Type Use  PIM PAM POM  CHPIDs
----------------------------------------------------------------------
0.0.1a10 0.0.0000  0000/00 3832/02 yes  80  80  ff   00000000 00000000
0.0.1a12 0.0.0001  0000/00 3832/02 yes  80  80  ff   00000000 00000000