VERITAS Volume Manager 3.5 Administrator's Guide (September 2002)

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Creating Volumes
7
Introduction
This chapter describes how to create volumes in VERITAS Volume Manager (VxVM).
Volumes are logical devices that appear as physical disk partition devices to data
management systems. Volumes enhancerecoveryfromhardwarefailure,data availability,
performance, and storage configuration.
Volumes arecreated to take advantage of the VxVMconcept ofvirtual disks.A filesystem
can be placed on the volume to organize the disk space with files and directories. In
addition, you can configure applications such as databases to organize data on volumes.
Note Disks and disk groups must be initialized and definedto VxVM beforevolumes can
be created from them. See “Administering Disks” on page 53 and “Creating and
Administering Disk Groups” on page 107 for more information.
Types of Volume Layouts
VxVM allows you to create volumes with the following layout types:
◆ Concatenated—A volume whose subdisks are arranged both sequentially and
contiguously within a plex. Concatenation allows a volume to be created from
multiple regions of oneor moredisks if there is not enoughspace for an entire volume
on asingle region ofa disk. For moreinformation, see “Concatenation andSpanning”
on page 15.
◆ Striped—A volume with data spread evenly across multiple disks. Stripes are
equal-sized fragments that are allocated alternately and evenly to the subdisks of a
single plex. There must be at least two subdisks in a striped plex, each of which must
exist on a different disk. Throughput increases with the number of disks across which
a plex is striped. Striping helps to balance I/O load in cases where high traffic areas
exist on certain subdisks. For more information, see “Striping (RAID-0)” on page 17.