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

VxVM provides easy-to-use online disk storage management for computing

environments and Storage Area Network (SAN) environments. By supporting the

Redundant Array of Independent Disks (RAID) model, VxVM can be configured

to protect against disk and hardware failure, and to increase I/O throughput.

Additionally, VxVM provides features that enhance fault tolerance and fast

recovery from disk failure or storage array failure.

VxVM overcomes restrictions imposed by hardware disk devices and by LUNs by

providing a logical volume management layer. This allows volumes to span multiple

disks and LUNs.

VxVM provides the tools to improve performance and ensure data availability

and integrity. You can also use VxVM to dynamically configure storage while the

system is active.

VxVM and the operating system

VxVM operates as a subsystem between your operating system and your data

management systems, such as file systems and database management systems.

VxVM is tightly coupled with the operating system. Before a disk or LUN can be

brought under VxVM control, the disk must be accessible through the operating

system device interface. VxVM is layered on top of the operating system interface

services, and is dependent upon how the operating system accesses physical disks.

VxVM is dependent upon the operating system for the following functionality:

■ operating system (disk) devices

■ device handles

■ VxVM Dynamic Multi-Pathing (DMP) metadevice

VxVM relies on the following constantly-running daemons and kernel threads

for its operation:

The VxVM configuration daemon maintains disk and

group configurations and communicates configuration

changes to the kernel, and modifies configuration

information stored on disks.

vxconfigd

VxVM I/O kernel threads provide extended I/O operations

without blocking calling processes. By default, 16 I/O

threads are started at boot time, and at least one I/O

thread must continue to run at all times.

vxiod

Understanding Veritas Volume Manager

VxVM and the operating system