VERITAS Volume Manager 3.5 Administrator's Guide (September 2004)

Understanding VERITAS Volume Manager
Device Discovery
Chapter 1 7
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 Device Discovery services enables you to add
support dynamically for new disk arrays. This operation, which uses a
facility called the Device Discovery Layer (DDL), is achieved without the
need for a reboot.
This means that you can dynamically add a new disk array to a host, and
run a command which scans the operating system’s device tree for all the
attached disk devices, and reconfigures DMP with the new device
database. For more information, see “Administering the Device Discovery
Layer” on page 71.
Enclosure-Based Naming
Enclosure-based naming provides an alternative to the disk device
naming described in “Physical Objects—Physical Disks” on page 4. This
allows disk devices to be named for enclosures rather than for the
controllers through which they are accessed. In a Storage Area Network
(SAN) that uses Fibre Channel hubs or fabric switches, information
about disk location provided by the operating system may not correctly
indicate the physical location of the disks. For example, c#t#d# naming
assigns controller-based device names to disks in separate enclosures
that are connected to the same host controller. Enclosure-based naming
allows VxVM to access enclosures as separate physical entities. By
configuring redundant copies of your data on separate enclosures, you
can safeguard against failure of one or more enclosures.