Virtual SCSI allows client logical partitions to share disk storage and tape or optical devices that are assigned to the Virtual I/O Server logical partition.
Disk, tape, or optical devices attached to physical adapters in the Virtual I/O Server logical partition can be shared by one or more client logical partitions. The Virtual I/O Server is a standard storage subsystem that provides standard SCSI-compliant LUNs. The Virtual I/O Server is capable of exporting a pool of heterogeneous physical storage as a homogeneous pool of block storage in the form of SCSI disks. The Virtual I/O Server is a localized storage subsystem. Unlike typical storage subsystems that are physically located in the SAN, the SCSI devices exported by the Virtual I/O Server are limited to the domain within the server. Therefore, although the SCSI LUNs are SCSI compliant, they might not meet the needs of all applications, particularly those that exist in a distributed environment.
The following SCSI peripheral device types are supported:
- Disk backed by logical volume
- Disk backed by physical volume
- Disk backed by file
- Optical CD-ROM, DVD-RAM, and DVD-ROM
- Optical DVD-RAM backed by file
- Tape devices
Virtual SCSI is based on a client-server relationship. The Virtual I/O Server owns the physical resources as well as the virtual SCSI server adapter, and acts as a server, or SCSI target device. The client logical partitions have a SCSI initiator referred to as the virtual SCSI client adapter, and access the virtual SCSI targets as standard SCSI LUNs. You configure the virtual adapters by using the HMC or Integrated Virtualization Manager. The configuration and provisioning of virtual disk resources is performed by using the Virtual I/O Server. Physical disks owned by the Virtual I/O Server can be either exported and assigned to a client logical partition as a whole or can be partitioned into parts, such as logical volumes or files. The logical volumes and files can then be assigned to different logical partitions. Therefore, using virtual SCSI, you can share adapters as well as disk devices. To make a physical volume, logical volume, or file available to a client logical partition requires that it be assigned to a virtual SCSI server adapter on the Virtual I/O Server. The client logical partition accesses its assigned disks through a virtual-SCSI client adapter. The virtual-SCSI client adapter recognizes standard SCSI devices and LUNs through this virtual adapter.
The following figure shows a standard virtual SCSI configuration.
