Veritas 4.1 Installation Guide (HP-UX 11i v3, February 2007)

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 configuration
information stored on the disks.
• vxiod – The VxVM I/O daemon provides extended I/O operations without blocking calling
processes.
• vxrelocd – The hot-relocation daemon monitors VxVM for events that affect redundancy,
and perform hot-relocation to restore redundancy.
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.
• Logical Objects
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 that can be used by the administrator to reference that disk group. Each disk
group 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 of a physical disk.
VxVM allocates a set of contiguos 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 to applications, databases, and file systems
like a physical disk device. 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.
Volume Layouts in VxVM
A volume layout is defined by the association of a volume to one or more plexes, each of which
map to subdisks. VxVM supports two different types of volume layout:
• Non-Layered
• Layered
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