Volumes are created to take advantage of the Volume Manager
concept of virtual disks. A file system can be placed on the volume
to organize the disk space with files and directories. In addition,
applications such as databases can be used to organize data on volumes.
The Volume Manager allows you to create volumes with the following layout
types:
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The vxassist command provides the simplest way to create new volumes.
To create a volume, use the following command:
# vxassist make volume_name length [attributes] |
where make is the keyword for volume creation, volume_name is a name you give to the volume, and length specifies the number of sectors (by default) in the
volume. The length can be specified in kilobytes, megabytes, or
gigabytes by using a suffix character of k, m, or g, respectively. See the vxintro(1M) manual page for more information on specifying
units of length when creating volumes. Additional attributes can
be specified, as appropriate.
By default, the vxassist command creates volumes in the rootdg disk group. Another disk group can be specified
by including -g diskgroup in the vxassist command line.
Creating a volume in the disk group rootdg creates two device node files that can be used
to access the volume:
/dev/vx/dsk/volume_name (the block device node for the volume)
/dev/vx/rdsk/volume_name (the raw device node for the volume)
For volumes in rootdg and disk groups other than rootdg, these names include the disk group name, as follows:
/dev/vx/dsk/diskgroup_name/volume_name
/dev/vx/rdsk/diskgroup_name/volume_name
The following section, “Creating a Concatenated Volume” describes the simplest way to create a (default)
volume. Later sections describe how to create volumes with specific
attributes.
Creating a Concatenated Volume |
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By default, the vxassist command creates a concatenated volume that uses
one or more sections of disk space. On a fragmented disk, this allows
you to put together a volume larger than any individual section
of free disk space available.
If there is not enough space on a single disk, vxassist creates a spanned volume. A spanned volume is
a concatenated volume with sections of disk space spread across
more than one disk. A spanned volume can be larger than the single
largest disk, since it takes space from more than one disk.
Creating a Concatenated Volume on
Any Disk
If no disk is specified, the Volume Manager selects a disk
on which to create the volume.
To create a concatenated, default volume, use the following
command:
# vxassist make volume_name length |
where volume_name is the name of the volume and length specifies the length of the volume in sectors (unless
another unit of size is specified with a suffix character).
When you resize a volume, you can specify the length of a
new volume in sectors, kilobytes, megabytes, or gigabytes. The unit
of measure is added as a suffix to the length (s, m, k, or g). If no unit is specified, sectors are assumed.
For example. to create the volume voldefault with a length of 10 megabytes, use the following
command:
# vxassist make voldefault 10m
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Creating a Concatenated Volume on
a Specific Disk
The Volume Manager automatically selects the disk(s) each
volume resides on, unless you specify otherwise. If you want a volume
to reside on a specific disk, you must designate that disk for the
Volume Manager. More than one disk can be specified.
To create a volume on a specific disk, use the following command:
# vxassist make volume_name length diskname [...] |
For example, to create the volume volspecific on disk03, use the following command:
# vxassist make volspecific 3m disk03
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Creating a Striped Volume |
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A striped volume contains at least one plex that consists
of two or more subdisks located on two or more physical disks. For
more information on striping, see “Striping (RAID-0)” and “Striping Guidelines”.
To create a striped volume, use the following command:
# vxassist make volume_name length layout=stripe |
For example, to create the striped volume volzebra, use the following command:
# vxassist make volzebra 10m layout=stripe |
This creates a striped volume with the default stripe unit
size on the default number of disks.
Indicate the disks on which the volumes are to be created
by specifying the disk names at the end of the command line. For
example, to create a 30 megabyte striped volume on three specific
disks (disk03, disk04, and disk05), use the following command:
# vxassist make stripevol 30m layout=stripe disk03 disk04\
disk05
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