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Manual: Volume Manager 4.1 Administrator's Guide   

Using vxassist

You can use the vxassist utility to create and modify volumes. Specify the basic requirements for volume creation or modification, and vxassist performs the necessary tasks.

The advantages of using vxassist rather than the advanced approach include:

  • Most actions require that you enter only one command rather than several.
  • You are required to specify only minimal information to vxassist. If necessary, you can specify additional parameters to modify or control its actions.
  • Operations result in a set of configuration changes that either succeed or fail as a group, rather than individually. System crashes or other interruptions do not leave intermediate states that you have to clean up. If vxassist finds an error or an exceptional condition, it exits after leaving the system in the same state as it was prior to the attempted operation.

The vxassist utility helps you perform the following tasks:

  • Creating volumes.
  • Creating mirrors for existing volumes.
  • Growing or shrinking existing volumes.
  • Backing up volumes online.
  • Reconfiguring a volume's layout online.

vxassist obtains most of the information it needs from sources other than your input. vxassist obtains information about the existing objects and their layouts from the objects themselves.

For tasks requiring new disk space, vxassist seeks out available disk space and allocates it in the configuration that conforms to the layout specifications and that offers the best use of free space.

The vxassist command takes this form:


# vxassist [options] keyword volume [attributes...]

where keyword selects the task to perform. The first argument after a vxassist keyword, volume, is a volume name, which is followed by a set of desired volume attributes. For example, the keyword make allows you to create a new volume:


# vxassist [options] make volume length [attributes]

The length of the volume can be specified in sectors, kilobytes, megabytes, or gigabytes using a suffix character of s, k, m, or g. If no suffix is specified, the size is assumed to be in sectors. See the vxintro(1M) manual page for more information on specifying units.

Additional attributes can be specified as appropriate, depending on the characteristics that you wish the volume to have. Examples are stripe unit width, number of columns in a RAID-5 or stripe volume, number of mirrors, number of logs, and log type.

Note   Note    By default, the vxassist command creates volumes in a default disk group according to the rules given in Rules for Determining the Default Disk Group. To use a different disk group, specify the -g diskgroup option to vxassist.

For details of available vxassist keywords and attributes, refer to the vxassist(1M) manual page.

The section, Creating a Volume on Any Disk describes the simplest way to create a volume with default attributes. Later sections describe how to create volumes with specific attributes. For example, Creating a Volume on Specific Disks describes how to control how vxassist uses the available storage space.

Setting Default Values for vxassist

The default values that the vxassist command uses may be specified in the file /etc/default/vxassist. The defaults listed in this file take effect if you do not override them on the command line, or in an alternate defaults file that you specify using the -d option. A default value specified on the command line always takes precedence. vxassist also has a set of built-in defaults that it uses if it cannot find a value defined elsewhere.

Note   Note    You must create the /etc/default directory and the vxassist default file if these do not already exist on your system.

The format of entries in a defaults file is a list of attribute-value pairs separated by new lines. These attribute-value pairs are the same as those specified as options on the vxassist command line. Refer to the vxassist(1M) manual page for details.

To display the default attributes held in the file /etc/default/vxassist, use the following form of the vxassist command:

# vxassist help showattrs

The following is a sample vxassist defaults file:


#  By default:
#  create unmirrored, unstriped volumes
#  allow allocations to span drives
#  with RAID-5 create a log, with mirroring don't create a log
#  align allocations on cylinder boundaries
layout=nomirror,nostripe,span,nocontig,raid5log,noregionlog,
diskalign
#  use the fsgen usage type, except when creating RAID-5 volumes
 usetype=fsgen
# allow only root access to a volume
 mode=u=rw,g=,o=
 user=root
 group=root
# when mirroring, create two mirrors
 nmirror=2
# for regular striping, by default create between 2 and 8 stripe 
# columns
 max_nstripe=8
 min_nstripe=2
#  for RAID-5, by default create between 3 and 8 stripe columns
 max_nraid5stripe=8
 min_nraid5stripe=3
#  by default, create 1 log copy for both mirroring and RAID-5 volumes
 nregionlog=1
 nraid5log=1
#  by default, limit mirroring log lengths to 32Kbytes
 max_regionloglen=32k
#  use 64K as the default stripe unit size for regular volumes
 stripe_stwid=64k
#  use 16K as the default stripe unit size for RAID-5 volumes
 raid5_stwid=16k
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Product: Volume Manager Guides  
Manual: Volume Manager 4.1 Administrator's Guide  
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