When a volume is mapped, IBM Spectrum Virtualize software automatically assigns the next available SCSI ID if none is specified. In addition, a unique identifier, called the UID , is on each volume. 

You can allocate the operating system volume of the SAN boot as the lowest SCSI ID (zero for most hosts), and then allocate the various data disks. If you share a volume among multiple hosts, consider controlling the SCSI ID so that the IDs are identical across the hosts. This consistency ensures ease of management at the host level and prevents potential issues during IBM Spectrum Virtualize updates and even node reboots, mostly for ESX operating systems. 

If you are using image mode to migrate a host to IBM Spectrum Virtualize, allocate the volumes in the same order that they were originally assigned on the host from the back-end storage. 

The lshostvdiskmap  command displays a list of VDisk (volumes) that are mapped to a host. These volumes are recognized by the specified host. Example 7-1 shows the syntax of the lshostvdiskmap  command that is used to determine the SCSI ID and the UID of volumes. 

Example 7-1 The lshostvdiskmap command 

svcinfo lshostvdiskmap -delim 

Example 7-2 shows the results of using the lshostvdiskmap  command. 

svcinfo lsvdiskhostmap -delim : EEXCLS_HBin01 id:name: SCSI_id :host_id:host_name:wwpn:vdisk_UID 950:EEXCLS_HBin01:14:109:HDMCENTEX1N1:10000000C938CFDF:600507680191011D4800000000000466 950:EEXCLS_HBin01:14:109:HDMCENTEX1N1:10000000C938D01F:600507680191011D4800000000000466 950:EEXCLS_HBin01: 13 :110:HDMCENTEX1N2:10000000C938D65B:600507680191011D4800000000000466 950:EEXCLS_HBin01: 13 :110:HDMCENTEX1N2:10000000C938D3D3:600507680191011D4800000000000466 950:EEXCLS_HBin01:14:111:HDMCENTEX1N3:10000000C938D615:600507680191011D4800000000000466 950:EEXCLS_HBin01:14:111:HDMCENTEX1N3:10000000C938D612:600507680191011D4800000000000466 950:EEXCLS_HBin01:14:112:HDMCENTEX1N4:10000000C938CFBD:600507680191011D4800000000000466 950:EEXCLS_HBin01:14:112:HDMCENTEX1N4:10000000C938CE29:600507680191011D4800000000000466 950:EEXCLS_HBin01:14:113:HDMCENTEX1N5:10000000C92EE1D8:600507680191011D4800000000000466 950:EEXCLS_HBin01:14:113:HDMCENTEX1N5:10000000C92EDFFE:600507680191011D4800000000000466 

Note:  Example 7-2 shows the same volume mapped to five different hosts, but host 110 has a different SCSI ID from the other four hosts. This is an example of a non-recommended practice which can lead to loss of access in some situations due to SCSI ID mismatch. 

In this example,  VDisk 10  has a unique device identifier (UID, which is represented by the UID field) of 6005076801958001500000000000000A  (see Example 7-3), but the SCSI_ id that host2 uses for access is 0 . 

id:name:SCSI_id:vdisk_id:vdisk_name:wwpn:vdisk_UID 2:host2:0:10: vdisk10 :0000000000000ACA: 6005076801958001500000000000000A 2:host2:1:11:vdisk11:0000000000000ACA:6005076801958001500000000000000B 2:host2:2:12:vdisk12:0000000000000ACA:6005076801958001500000000000000C 

