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

The hot-relocation daemon monitors VxVM for events
that affect redundancy, and performs hot-relocation to
restore redundancy. If thin provision disks are configured
in the system, then the storage space of a deleted volume
is reclaimed by this daemon as configured by the policy.
vxrelocd
How data is stored
Several methods are used to store data on physical disks. These methods organize
data on the disk so the data can be stored and retrieved efficiently. The basic
method of disk organization is called formatting. Formatting prepares the hard
disk so that files can be written to and retrieved from the disk by using a
prearranged storage pattern.
Two methods are used to store information on formatted hard disks:
physical-storage layout and logical-storage layout. VxVM uses the logical-storage
layout method.
See “How VxVM handles storage management” on page 21.
How VxVM handles storage management
VxVM uses the following types of objects to handle storage management:
Physical disks, LUNs (virtual disks implemented in hardware), or
other hardware with block and raw operating system device
interfaces that are used to store data.
See “Physical objects” on page 21.
Physical 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.
See “Virtual objects” on page 27.
Virtual objects
Physical objects
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
21Understanding Veritas Volume Manager
How VxVM handles storage management