Veritas 5.0.1 Installation Guide HP-UX 11i v3 (5900-2464, September 2012)

VxVM Daemons
VxVM relies on the following daemons for its operation:
• vxconfigd – The VxVM configuration daemon maintains disk and disk group configuration
information, communicates configuration changes to the kernel, and modifies the configuration
information stored on the disks.
• vxiod – The VxVM I/O daemon provides extended I/O operations without blocking the
calling processes.
• vxrelocd – The hot-relocation daemon monitors VxVM for events that affect redundancy,
and performs hot-relocation to restore redundancy.
• vxattachd – The vxattachd daemon handles automatic reattachment and resynchronization
for plexes.
VxVM Objects
VxVM supports the following types of objects:
• Physical Objects
Physical disks or other hardware with block and raw operating system device interfaces that
are used to store data.
• Virtual Objects
The virtual objects in VxVM include the following:
◦ Disk Group
A group of disks that share a common configuration. A configuration consists of a set of
records describing objects (including disks, volumes, plexes, and subdisks) that are
associated with one particular disk group. Each disk group has an administrator-assigned
name, which can be used by the administrator to reference that disk group. Each disk
group also has an internally defined unique disk group ID, which is used to differentiate
two disk groups with the same administrator-assigned name.
◦ VM Disks
When you place a physical disk under VxVM control, a VM disk is assigned to the physical
disk. Each VM disk corresponds to one physical disk. A VM disk is under VxVM control
and is usually in a disk group.
◦ Subdisks
A VM disk can be divided into one or more subdisks. Each subdisk represents a specific
portion of a VM disk, which in turn is mapped to a specific region in a physical disk.
VxVM allocates a set of contiguous blocks for a subdisk.
◦ Plexes
VxVM uses subdisks to build virtual objects called plexes. A plex consists of one or more
subdisks located on one or more physical disks.
◦ Volumes
A volume is a virtual disk device that appears like a physical disk device to applications,
databases, and file systems. However, VxVM volumes do not have the physical limitations
of a physical disk device. A volume consists of one or more plexes, each holding a copy
of the selected data in the volume.
14 Introduction