Veritas Volume Manager 5.1 SP1 Administrator"s Guide (5900-1506, April 2011)

Figure 1-2 shows how VxVM represents the disks in a disk array as several volumes
to the operating system.
Figure 1-2
How VxVM presents the disks in a disk array as volumes to the
operating system
Veritas Volume Manager
Physical disks
Operating system
Volumes
Disk 1 Disk 2 Disk 3 Disk 4
Data can be spread across several disks within an array, or across disks spanning
multiple arrays, to distribute or balance I/O operations across the disks. Using
parallel I/O across multiple disks in this way improves I/O performance by
increasing data transfer speed and overall throughput for the array.
Multiple paths to 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).
See “How DMP works” on page 141.
HP-UX 11i v3 provides its own native multi-pathing solution in addition to the
Dynamic Multi-Pathing (DMP) that is used by VxVM. These two multi-pathing
solutions can coexist on the same system.
See “DMP coexistence with HP-UX native multi-pathing” on page 147.
23Understanding Veritas Volume Manager
How VxVM handles storage management