Veritas Volume Manager 4.1 Administrator's Guide (HP-UX 11i v3, February 2007)

How VxVM Handles Storage Management
4 VERITAS Volume Manager Administrator’s Guide
How VxVM Handles Storage Management
VxVM uses two types of objects to handle storage management: physical objects and virtual
objects.
◆ Physical Objects—Physical Disks or other hardware with block and raw operating
system device interfaces that are used to store data.
◆ Virtual Objects—When one or more physical disks are brought under the control of
VxVM, it creates virtual objects called volumes on those physical disks. Each volume
records and retrieves data from one or more physical disks. Volumes are accessed by
file systems, databases, or other applications in the same way that physical disks are
accessed. Volumes are also composed of other virtual objects (plexes and subdisks)
that are used in changing the volume configuration. Volumes and their virtual
components are called virtual objects or VxVM objects.
Physical Objects—Physical Disks
A physical disk is the basic storage device (media) where the data is ultimately stored. You
can access the data on a physical disk by using a device name to locate the disk. The
physical disk device name varies with the computer system you use. Not all parameters
are used on all systems. Typical device names are of the form c#t#d#, where:
◆ c# specifies the controller
◆ t# specifies the target ID
◆ d# specifies the disk
The figure, “Physical Disk Example” on page 4, shows how a physical disk and device
name (devname) are illustrated in this document. For example, device name c0t0d0 is the
entire hard disk connected to controller number 0 in the system, with a target ID of 0, and
physical disk number 0.
Physical Disk Example
VxVM writes identification information on physical disks under VxVM control (VM
disks). VxVM disks can be identified even after physical disk disconnection or system
outages. VxVM can then re-form disk groups and logical objects to provide failure
detection and to speed system recovery.
devname