HP Veritas Volume Manager 5.0 -UX 11i v3 manual Enclosure-based naming

Understanding Veritas Volume Manager

How VxVM handles storage management

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Device Discovery service 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 85.

Enclosure-based naming

Enclosure-based naming provides an alternative to the disk device naming described in “Physical objects—physical disks” on page 20. 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.

In a typical SAN environment, host controllers are connected to multiple enclosures in a daisy chain or through a Fibre Channel hub or fabric switch as illustrated in Figure 1-3.