Adding a Virtual Disk on an Auxiliary Virtual SCSI Controller to a Virtual Machine Moves Other Devices to New PCI Slots

This is most often a problem when you add or remove a virtual disk on an auxiliary virtual SCSI controller.

The VMware vPlatform uses a standard plan to arrange the slot order of virtual devices in a virtual machine. Currently it is not possible to specify the load order of individual virtual PCI devices (for example, scsi0 goes in PCI slot 0x11, and so on).

Virtual PCI devices are populated into the PCI slots in a virtual machine using a predefined scan order:

1. PCI 0x00:0x0f.0x00 (PCI bus zero, slot fifteen, function zero) contains the VMware SVGA II video adapter. This maps to slot 1 on the virtual hardware. It is not possible to disable the virtual video adapter device. Based on availability, the remaining five virtual PCI slots are filled.
2. All virtual SCSI controllers are added in based on the numbering key (scsi#), starting at PCI 0x00:0x10.0x00 (PCI bus zero, slot sixteen, function zero) with the lowest numbered virtual SCSI controller.
3. After all virtual SCSI controllers are populated, the virtual Ethernet controllers are added.
4. Finally, the virtual sound card (if available and configured) is populated in.

Adding or removing a virtual SCSI controller, for example, causes the devices further down in the scan order (virtual Ethernet controllers and the virtual sound card) to move to new virtual PCI slot locations.

Bringing up virtual PCI devices in this order preserves the virtual PCI slot mapping for the first virtual SCSI controller at all times. The first virtual SCSI controller is typically used as the boot SCSI controller, and many operating systems rely on that SCSI controller being in a fixed location on the PCI bus.