DMP overview

The Dynamic Multi-Pathing option adds additional fault tolerance to disk storage by making use of multiple paths between a computer and a disk in a storage array. A path is a connection between the computer and the storage array's disks and consists of a host adapter and a SCSI bus connection to one or more SCSI disks or a fiber optic channel that is connected to a hub, switch, or array. Thus, multiple paths are made possible by connecting two or more host bus adapters with either SCSI or fiber optic cabling to the storage array. The Dynamic Multi-Pathing software manages the multiple paths so that the data on each of the array's disks is accessible to the host computer. If a path to a disk fails, Dynamic Multi-Pathing automatically transmits data to and from the disk over an alternate path.

The paths on an array are set up to work in two ways - either in Active/Active mode, which provides load balancing of the data between multiple paths, or in Active/Passive mode, in which only one path is active and any remaining paths are backups.

SFW offers Dynamic Multi-Pathing as DMP device-specific modules (DSMs).

Note:

Windows Management Instrumentation (WMI) is a required service for the MPIO feature to work. Without this service, the MPIO Provider does not load and MPIO objects are not displayed on the VEA console or CLI command outputs. MPIO operations too cannot be performed in absence of WMI service.

DMP DSMs are designed to support a multi-path disk storage environment set up with the Microsoft Multipath I/O (Microsoft MPIO) solution. DMP DSMs work effectively with Windows to provide a fault tolerant multi-path disk storage environment. DMP DSMs have the following benefits:

Basic disks are supported if SCSI-3 registry support is not enabled for DMP DSMs. If SCSI-3 registry is enabled for DMP DSMs for an attached array, then existing basic disks should be upgraded to dynamic disks before placing them under control of DMP DSMs.

For DMP DSMs, Boot and data volumes are supported on the same bus/HBAs for non-clustered servers if the Boot from SAN recommendations from Microsoft is followed. DMP DSMs are not supported with Fibre Channel port drivers, Fibre Channel SCSI Miniport drivers or boot or cluster disks on the same bus/HBAs.