can anyone tell me why scsi (0:7) is missing in vm virtual device node even it is not there in any controller means scsi (1:7) os also missing from there.
The virtual SCSI adapter requires a SCSI ID and 7 is reserved for it.
for what purpose scsi adapter requires it?
Think of the SCSI bus as a network with 16 addresses - every device on that bus needs an address including the SCSI adapter =
Like disks or other SCSI devices, the host adapter is a SCSI device too. The reason for address 7 is most likely due to the fact that early SCSI adapters only had 8 addresses (0 trough 7) and the highest address was used for the host adapter by default.
André
"By default, the SCSI controller is assigned to virtual device node (z:7), so that device node is unavailable for hard disks or SCSI devices."
SCSI Controller Configuration
To access virtual disks and SCSI devices, a virtual machine uses virtual SCSI controllers. These virtual controllers appear to a virtual machine as different types of controllers, including BusLogic Parallel, LSI Logic Parallel, LSI Logic SAS, and VMware Paravirtual SCSI. You can add a SCSI controller, change the SCSI controller type, and select bus sharing for a virtual machine.
Each virtual machine can have a maximum of four SCSI controllers. The default SCSI controller is numbered as 0. When you create a virtual machine, the default hard disk is assigned to the default SCSI controller 0 at bus node (0:0).
When you add SCSI controllers, they are numbered sequentially 1, 2, and 3. If you add a hard disk or SCSI device to a virtual machine after virtual machine creation, it is assigned to the first available virtual device node on the default SCSI Controller, for example (0:1).
If you add a SCSI controller, you can reassign an existing or new hard disk, or a SCSI device, to that controller. For example, you can assign the device to (1:z ), where 1 is SCSI Controller 1 and z is a virtual device node from 0 to 15.
By default, the SCSI controller is assigned to virtual device node (z:7), so that device node is unavailable for hard disks or SCSI devices.