vgmodify(1M)

NAME

vgmodify — handle physical volume size changes and modify configuration parameters of an existing LVM volume group

SYNOPSIS

Set Specified Parameters

/usr/sbin/vgmodify [-B bootable] [-e max_pe] [-l max_lv] [-n] [-p max_pv] [-r] [-v] vg_name [pv_path...]

Optimize the Volume Group Settings

/usr/sbin/vgmodify -o [-B bootable] [-r] [-v] vg_name [pv_path...]

Display a Table of Optimized Possible Volume Group Settings

/usr/sbin/vgmodify -t [-B bootable] [-n] [-v] vg_name [pv_path...]

Remarks

If vgmodify is interrupted while it is committing the configuration changes onto the disks, it may be necessary to re-apply the configuration to all the physical volumes. The /etc/lvmconf/VG_restore script must used to accomplish this. To apply the new configuration, enter the following:
/etc/lvmconf/VG_restore /etc/lvmconf/VG.conf
Or to apply the old/original configuration, enter the following:
/etc/lvmconf/VG_restore /etc/lvmconf/VG.conf.old
The root/boot volume group must be booted into maintenance mode before making changes (see boot(1M)).
The volume group must be removed from membership in a high availability cluster before making changes (see vgchange(1M)).
To expand the LVM configuration data to its maximum size it may be necessary to reallocate the first physical extent from each physical volume from user to LVM configuration data. This will only be possible if the first extent is made free (see pvmove(1M)) and PE renumbering is enabled via the -n option.
The LVM configuration data size is limited to the volume group extent size. Therefore, a maximum of one physical extent from each physical volume can be reallocated from user data regardless of how many times vgmodify is used on the volume group.
The attributes of an lvmconf file can be viewed using the -v option of vgcfgrestore (see vgcfgrestore(1M)).
To take advantage of a physical volume size increase, it may be necessary to run vgmodify to increase the maximum number of physical extents for the volume group.
In general, a smaller number of physical volumes allows a larger number of physical extents. Likewise, a larger number of physical volumes constrains to a smaller number of physical extents.
The detection of physical volume size changes (LUN size expansion or contraction) is automatic, with the handling taking place unless the -r or -t options have been used.
The changing of physical volume type (boot to non-boot and vice versa) is selected via the -B option and by specifying a list of physical volumes. Otherwise no physical volume type changes are performed.

DESCRIPTION

The vgmodify command allows the user to modify an existing volume group (vg_name). The following changes can be performed:

Detect and handle physical volume size changes.
Modify the maximum number of physical extents that can be allocated per physical volume (max_pe setting) (see vgcreate(1M) -e).
Modify the maximum number of physical volumes that the volume group can contain (max_pv setting) (see vgcreate(1M) -p).
Modify the maximum number of logical volumes that the volume group can contain (max_lv setting) (see vgcreate(1M) -l).
Change a physical volume type from boot to non-boot or vice versa (see pvcreate(1M) -B). Note that making a physical volume non-bootable will increase the space available on that device for LVM configuration data. However, even a single bootable physical volume in the volume group will restrict the max_pv and max_pe settings available.

All the physical volumes associated with the volume group must be available for the vgmodify command to succeed.

The volume group can be active when reporting the configuration (-r) or displaying a table of available settings (-t). The volume group must be de-activated before vgmodify can perform any configuration changes (see vgchange(1M)).

If the command is interrupted before it completes, recovery steps might be required. See the Remarks section for details.

Options and Arguments

The vgmodify command recognizes the following options and arguments:

vg_name

The path name of a volume group.

pv_path

The character (raw) device path name of a physical volume that will become bootable or non-bootable based on the -B option. If type changes are not required then the pv_path list must be empty and the -B option must not be used.

-B bootable

Make the physical volumes specified in the pv_paths list bootable or non-bootable. bootable can have one of the following values:

y: Change pv_path list from non-bootable to bootable.
n: Change pv_path list from bootable to non-bootable.

See the description of the -B option in pvcreate(1M).

Making a physical volume non-bootable will increase the space available on that device for LVM configuration data. However to fully use that space all the physical volumes in the volume group should be non-bootable. A single bootable physical volume in the volume group will restrict the available configuration settings.

A physical volume can only be made bootable if either all extents on it are unused or it was previously converted from a bootable device and the space is still unused.

If a physical volume is being made bootable then use lvlnboot and mkboot to complete the process (see lvlnboot(1M) and mkboot(1M)).

-e max_pe

Set the maximum number of physical extents that can be allocated from any of the physical volumes in the volume group (see vgcreate(1M)) -e).

The maximum number of physical extents can range from the current highest physical extent in use on any physical volume in the volume group (1 if none in use) up to 65535.

The -t option displays a table of possible max_pe values for vg_name.

-l max_lv

Set the maximum number of logical volumes that the volume group is allowed to contain (see vgcreate(1M) -l).

The maximum number of logical volumes can range from the current highest logical volume number in use (1 if none in use) to 255.

Note that changing this value has little impact on the size of the LVM configuration data.

-n

Allow renumbering of physical extents on physical volumes. This only applies to physical volumes that have allocated extents. By default, physical extent numbers will be unchanged by vgmodify.

Renumbering physical extents changes the allocation of the first physical extent, if it is free, from user to LVM configuration data and vice-versa. This will often have a considerable impact on the space available for the LVM configuration data on each physical volume and, therefore, the possible settings for the volume group parameters.

No user data is moved during that process, only the LVM numbering of physical extents changes.

When the first extent is being reallocated from user to LVM configuration data, the physical extent numbers are decreased. This will only occur if the first extent is free. For example a logical volume using physical extents 10 to 20 from a physical volume that has its first extent reallocated to LVM configuration data will use the physical extents 9 to 19 after the modification. User data is not moved.

When the first extent is being reallocated from LVM configuration to user data, the physical extent numbers are increased. For example a logical volume using physical extents 10 to 20 from a physical volume that has its first extent re-allocated to user data will use the physical extents 11 to 21 after the modification. User data is not moved.

Not all configurations allow renumbering. If this is the case then an error will be reported and a recommendation to rerun without the -n option will be given.

-o

Optimize the volume group settings. The maximum number of extents and physical volumes are adjusted upwards, where possible, to make full use of the space reserved on each physical volume for the LVM configuration data.

This option cannot be used in conjunction with -l, -p, -n, -t, or -e.

-p max_pv

Set the maximum number of physical volumes that the volume group is allowed to contain (see vgcreate(1M) -p). The maximum number of physical volumes can range from the current number of physical volumes in the volume group to 255.

The -t option displays a table of possible max_pv values for vg_name.

-r

Report the effect of the other options being used. No changes will be made to the volume group.

This option can be used on an active volume group.

-t

Produce a table showing the optimal possible settings (max_pe, max_pv, and maximum disk size) for the volume group.

This option can be used with and without -n to see a complete list of possible optimal settings. In certain cases the optimal settings will not be influenced by the extent renumbering (-n) and a suitable message will then be reported.

Where adjacent max_pv values allow the same highest max_pe, only the highest max_pv is displayed; therefore, there may be gaps in the table. It is still possible to set a lower max_pv or max_pe than shown in the table but some of the LVM configuration space will not be used.

-t is normally used to obtain the arguments for future vgmodify command -e and/or -p options.

-v

Verbose. Be verbose in reporting.

EXTERNAL INFLUENCES

Environment Variables

LANG determines the language in which messages are displayed.

If LANG is not specified or is null, it defaults to "C" (see lang(5)).

If any internationalization variable contains an invalid setting, all internationalization variables default to "C" (see environ(5)).

RETURN VALUE

vgmodify returns one of the following values:

0: Successful completion.
>0: Error condition occurred.

EXAMPLES

Review the effect of setting a maximum of 6 physical volumes in the volume group:

vgmodify -p 6 -r /dev/vg02 

Set a maximum of 4000 physical extents per physical volume and a maximum of 50 physical volumes, and take advantage of extent renumbering if possible:

vgmodify -p 50 -e 4000 -n /dev/vg02 

Show a table of optimal possible settings for the volume group:

vgmodify -t /dev/vg02 

Show a table of optimal possible settings for the volume group taking advantage of extent renumbering if possible:

vgmodify -t -n /dev/vg02 

Show a table of optimal possible settings for the volume group, making the physical volume /dev/rdsk/c1t2d0 non-bootable:

vgmodify -t -B n /dev/vg02 /dev/rdsk/c1t2d0 

Review (do not change) the effect of choosing a maximum of 16 physical volumes, 8000 physical extents per physical volume, while making /dev/rdsk/c1t2d0 non-bootable (these values were selected from the table above) and be verbose:

vgmodify -p 16 -e 8000 -v -r -B n /dev/vg02 /dev/rdsk/c1t2d0 

Apply the settings just reviewed:

vgmodify -p 16 -e 8000 -v -B n /dev/vg02 /dev/rdsk/c1t2d0 

Verbosely review (do not change) the impact of optimizing the volume group settings:

vgmodify -v -r -o /dev/vg02 

Verbosely apply the changes that will result from optimizing the volume group settings:

vgmodify -v -o /dev/vg02 

If the vgmodify command is interrupted, restore the new configuration to all physical volumes in the volume group by entering:

/etc/lvmconf/vg02_restore /etc/lvmconf/vg02.conf 

WARNINGS

Changing the type of a bootable physical volume will prevent booting from this device and, therefore, may create an unbootable system.
Do not restore a physical volume from a backup file (lvmconf) produced prior to the latest vgmodify changes. Doing so will result in attempts to attach the device to the volume group failing and may lead to activation failures. If there is any doubt about the configuration in the lvmconf file, use vgcfgrestore -lv -f /etc/lvmconf/VG.conf to view the settings in the file.
If the vgmodify command is interrupted prior to completing its operation then restoration to all physical volumes in the volume group may be required. Use the restore script to accomplish this (see the Remarks section for more information).

FILES

/etc/lvmconf/VG.conf: Holds the latest (new) configuration for the volume group.
/etc/lvmconf/VG.conf.old: If vgmodify completes successfully, this file contains the same new configuration as /etc/lvmconf/VG.conf. If vgmodify was interrupted, this file contains the previous (old) configuration.
/etc/lvmconf/VG_restore: A script created by vgmodify before making any update, to be used if the vgmodify command is interrupted while committing the configuration changes to the physical volumes. See the Remarks section for its usage.