HP Veritas Volume Manager 5.0 -UX 11i v3 Device discovery, Multipathed disk arrays

22Understanding Veritas Volume Manager

How VxVM handles storage management

Figure 1-2	How VxVM presents the disks in a disk array as volumes to the
	operating system

Operating system

Veritas Volume Manager

Volumes

Physical disks
Disk 1	Disk 2	Disk 3	Disk 4

Multipathed disk arrays

Some disk arrays provide multiple ports to access their disk devices. These ports, coupled with the host bus adaptor (HBA) controller and any data bus or I/O processor local to the array, make up multiple hardware paths to access the disk devices. Such disk arrays are called multipathed disk arrays. This type of disk array can be connected to host systems in many different configurations, (such as multiple ports connected to different controllers on a single host, chaining of the ports through a single controller on a host, or ports connected to different hosts simultaneously).

HP-UX 11i v3 provides its own native multipathing solution in addition to the Dynamic Multipathing (DMP) feature that is used by VxVM. These two multipathing solutions can coexist on the same system. For more information, see “DMP coexistence with HP-UX native multipathing” on page 130.

Device discovery

Device discovery is the term used to describe the process of discovering the disks that are attached to a host. This feature is important for DMP because it needs to support a growing number of disk arrays from a number of vendors. In conjunction with the ability to discover the devices attached to a host, the