Hybrid vSCSI and NPIV Implementation

PowerVM Disk Virtualization

Virtual SCSI
vSCSI is a mechanism that allows the VIOS to present disk volumes to client LPARs across a virtualized SCSI connection. The VIOS owns the physical disk volumes and they can be locally attached or SAN based. The disk volumes are made available to client LPARs using the vSCSI interface and they appear as locally attached SCSI hard disk drives (hdisks) to the client LPAR.

N_Port ID Virtualization
NPIV provides an alternative method for disk virtualization on the VIOS. With NPIV, the physical Fibre-Channel adapter assigned to the VIOS can have 64 downstream virtual World Wide Names (WWN) associated with it. Virtual WWNs can then be assigned to client LPARs

Hybrid vSCSI and NPIV Implementation
VSCSI was the first disk-access virtualization technology provided with PowerVM. It works very well and is in use in many businesses. From a management perspective, VSCSI takes us back to the original UNIX server-implementation model where all disk is presented to the client LPAR as locally attached SCSI disk. The VIOS administrator manages all of the OS and data disk volumes, similar to when servers were configured with local SCSI disk drives. This can become quite a challenging task for servers with large amounts of data, as the responsibility for disk redundancy and backup falls upon their shoulders. One possible solution is to implement a hybrid disk-virtualization model.

With the hybrid model, vSCSI is used for the OS disks and NPIV is used for the data disks. This emulates the traditional environment where there was local SCSI OS disk and Fibre Channel-attached data disk. The client LPAR administrators see local SCSI disk for installation and management of the OS. All of the data disks are presented to the client LPAR through virtual Fibre-Channel connections on the NPIV interface. With regard to disk configuration and management, this allows the client LPAR administrator to focus on managing the OS disk volumes and the SAN administrator to focus on managing the data volumes.

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