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122 lines
5.5 KiB
Plaintext
122 lines
5.5 KiB
Plaintext
IBM Virtual SCSI Target (ibmvstgt)
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==================================
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Introduction
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------------
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The virtual SCSI (VSCSI) protocol as defined in [2] is a protocol that allows
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one logical partition (LPAR) to access SCSI targets provided by another LPAR.
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The LPAR that provides one or more SCSI targets is called the VIO server or
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VIOS. The ibmvstgt driver is a VIOS driver that makes it possible to access
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exported target devices via the VSCSI protocol.
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Setup
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-----
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After having configured the LPARs, boot the LPARs and load the ibmvstgt kernel
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module in the VIOS. After the target driver has been loaded, verify that a
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message similar to the following appears in the initiator kernel log:
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ibmvscsi 30000028: partner initialized
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ibmvscsi 30000028: host srp version: 16.a, host partition VIOS3-P6 (40), OS 2, max io 67108864
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ibmvscsi 30000028: sent SRP login
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ibmvscsi 30000028: SRP_LOGIN succeeded
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In the above log messages, the number 30000028 refers to the VIOS. The last
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two digits, 0x28, refer to the VIOS partition number (0x28 = 40).
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The next step is to decide which SCSI devices to export. Here is an example of
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a configuration in which 16 RAM disks have been exported (see also [1] for
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more information):
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$ cat /proc/scsi_tgt/vdisk/vdisk
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Name Size(MB) Block size Options File name T10 device id
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ram000 16 512 NV /dev/ram0 c726a6ab
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ram001 16 512 NV /dev/ram1 eca3eb12
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ram002 16 512 NV /dev/ram2 8e9fb87
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ram003 16 512 NV /dev/ram3 912b0e46
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ram004 16 512 NV /dev/ram4 c52a6cdf
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ram005 16 512 NV /dev/ram5 b3f98ada
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ram006 16 512 NV /dev/ram6 fb5fd9ce
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ram007 16 512 NV /dev/ram7 3285b724
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ram008 16 512 NV /dev/ram8 6a93ad6d
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ram009 16 512 NV /dev/ram9 f0c60f83
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ram010 16 512 NV /dev/ram10 f0c60f84
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ram011 16 512 NV /dev/ram11 f0c60f85
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ram012 16 512 NV /dev/ram12 f0c60f86
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ram013 16 512 NV /dev/ram13 f0c60f87
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ram014 16 512 NV /dev/ram14 f0c60f88
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ram015 16 512 NV /dev/ram15 f0c60f89
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After this step a LUN has to be assigned to each exported SCSI device. Some
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non-Linux initiator operating systems only accept LUN numbes that are
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multiples of 256 and require that the LUN addressing method is used. The LUN
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addressing method is only available for other groups than the Default group.
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Configuring such a group can be done e.g. as follows:
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vios_id="30000028"
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echo "add_group ${vios_id} LUN" >/proc/scsi_tgt/scsi_tgt
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echo "add ${vios_id}" >/proc/scsi_tgt/groups/${vios_id}/names
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lun=0
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for name in ram000 ram001 ram002 ram003 ram004 ram005 ram006 ram007 \
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ram008 ram009 ram010 ram011 ram012 ram013 ram014 ram015
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do
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lun=$((lun+256))
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echo "add $name $lun" >/proc/scsi_tgt/groups/${vios_id}/devices
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done
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In the above, the first echo command will create a group and will enable LUN
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addressing for that group. The second echo command tells SCST to use this
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group instead of the Default group for VSCSI. And the subsequent commands
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assign LUNs to the exported vdisks. The result of the above commands will
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be as follows:
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# cat /proc/scsi_tgt/groups/30000028/devices
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Device (host:ch:id:lun or name) LUN Options
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ram000 256
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ram001 512
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ram002 768
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ram003 1024
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ram004 1280
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ram005 1536
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ram006 1792
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ram007 2048
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ram008 2304
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ram009 2560
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ram010 2816
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ram011 3072
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ram012 3328
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ram013 3584
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ram014 3840
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ram015 4096
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After SCST has been configured, make the new configuration available to the
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initiator by rescanning the SCSI bus, e.g. as follows:
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# rescan-scsi-bus --hosts=2 --ids=0-31
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# lsscsi 2:
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[2:0:1:0] disk IBM VDASD blkdev 0001 /dev/sdb
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[2:0:2:0] disk IBM VDASD blkdev 0001 /dev/sdc
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[2:0:3:0] disk IBM VDASD blkdev 0001 /dev/sdd
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[2:0:4:0] disk IBM VDASD blkdev 0001 /dev/sde
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[2:0:5:0] disk IBM VDASD blkdev 0001 /dev/sdf
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[2:0:6:0] disk IBM VDASD blkdev 0001 /dev/sdg
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[2:0:7:0] disk IBM VDASD blkdev 0001 /dev/sdh
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[2:0:8:0] disk IBM VDASD blkdev 0001 /dev/sdi
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[2:0:9:0] disk IBM VDASD blkdev 0001 /dev/sdj
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[2:0:10:0] disk IBM VDASD blkdev 0001 /dev/sdk
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[2:0:11:0] disk IBM VDASD blkdev 0001 /dev/sdl
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[2:0:12:0] disk IBM VDASD blkdev 0001 /dev/sdm
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[2:0:13:0] disk IBM VDASD blkdev 0001 /dev/sdn
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[2:0:14:0] disk IBM VDASD blkdev 0001 /dev/sdo
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[2:0:15:0] disk IBM VDASD blkdev 0001 /dev/sdp
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[2:0:16:0] disk IBM VDASD blkdev 0001 /dev/sdq
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References
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----------
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[1] SCST Configuration Interface, Documentation/scst/README.scst.
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[2] Power.org Standard for Power Architecture Platform Requirements (PAPR)
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(Workstation, Server), Version 2.4, December 7, 2009, http://www.power.org.
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[3] Virtual I/O (VIO) and Virtualization, IBM Developerworks, 2010,
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http://www.ibm.com/developerworks/wikis/display/virtualization/VIO.
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