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voldg(8)
NAME
voldg - Manages Logical Storage Manager disk groups
SYNOPSIS
/sbin/voldg init groupname [medianame=] accessname...
[nconfig=config-copies | all | default] [minor=base-minor]
/sbin/voldg [-g diskgroup] [-f] reminor [diskgroup] new-base-minor
/sbin/voldg [-tfC] [-nnewname] import diskgroup
/sbin/voldg [-nnewname] [-hnewhostid] deport diskgroup...
/sbin/voldg [-g diskgroup] [-k] adddisk [medianame=] accessname...
/sbin/voldg [-g diskgroup] [-k] rmdisk [medianame]...
/sbin/voldg [-q] list [diskgroup...]
/sbin/voldg [-g diskgroup] [-qa] free [medianame...]
/sbin/voldg [-g diskgroup] [-q] spare [medianame...]
/sbin/voldg flush [diskgroup...]
/sbin/voldg [-g diskgroup] [-k] repldisk unassoc-medianame=spare-
medianame...
DESCRIPTION
The voldg utility performs basic administrative operations on disk groups.
Operations include the creation of disk groups, the addition of disks to a
disk group, and disk group imports and deports. The behavior of the voldg
utility depends upon the keyword specified as the first operand.
A groupname argument must be a disk group name.
A diskgroup argument can be either a disk group name or a disk group ID.
An accessname argument refers to a disk access name (also referred to as a
disk device name), as stored in the root configuration by the voldisk
utility (for example, dsk5). A medianame argument is an administrative
name used to define a disk within a disk group (for example, disk01).
KEYWORDS
Supported keywords for voldg are:
init
Defines a new disk group composed of the indicated disks, identified by
disk access names. This involves assigning an internal unique ID to the
group, storing a reference to the group on all of the named disks that
have a disk header, and storing a disk group record in the disk group's
configuration database. At least one of the disks specified must have
space allocated for a configuration copy.
If a medianame is specified for use with a particular disk, that
medianame will name the disk media record used to reference the disk
within the disk group (for operations such as rmdisk and subdisk
creations). If no medianame is specified, the disk media name defaults
to accessname See voldisk(8) for a discussion of definition and
initialization of disk access records.
The init operation can be used to initialize a root disk group
configuration, which is identified by the special name rootdg. Disks
should be initialized and added to the disk group as the first
operations after creating rootdg.
If the autoconfiguration functionality of LSM is disabled, some or all
disks added to the rootdg disk group should also be added to the
/etc/vol/volboot bootstrap file (see voldctl(8)).
The nconfig attribute can be used to configure the number of
configuration database copies and kernel log copies that are maintained
for a disk group.
The value of config-copies is either a decimal number (including 0 or
-1) or a setting of all or default.
A value of all or -1 signifies that all configuration or log copies on
all disks in the disk group will be maintained. A value of default or 0
(the default value) signifies that the Logical Storage Manager will
manage copies that are distributed in a reasonable pattern throughout
the disks and controllers on the system. Any other number signifies
that a particular number of copies should be maintained (or all copies,
if that number is larger than the number of available configuration or
log copies on all disks).
When a specific number (or default) is requested, configuration copies
are scattered approximately evenly through the disk controllers on the
system. If SCSI disks with multiple disks per target are found, each
such target is treated similarly to a controller (that is,
configuration copies are evenly distributed between such targets). With
the default policy, one configuration or log copy is maintained for
each controller, and one configuration or log copy is also maintained
for each SCSI target that has multiple disks; if this does not result
in allocating at least 4 copies, additional copies are spread through
the controllers and targets.
Refer to voldisk(8) for more information on configuration and log
copies, and for information on how to create them.
Note
If a policy other than all is used, some disks will not have up-to-
date, online configuration and log copies. As a result, it is
possible that some number of disk failures will leave a disk group
unusable, even if some disks in the disk group remain usable. The
default policy allocates a sufficient number of copies, in a
sufficient spread of locations, that such a scenario is very
unlikely to occur.
minor=base-minor
Since disk groups can be moved between systems, it is desirable that
device numbers used for volumes be allocated in separate ranges for
each disk group. That way, an administrator can choose ranges such that
all disk groups in a group of machines can be moved around without
causing device number collisions. Collisions may occur because the
Logical Storage Manager stores device numbers in disk group
configurations, so that the same numbers can be used after a reboot
(which is necessary for use with NFS, which requires persistency of
device numbers). If two systems use the same device numbers for a set
of volumes, and if a disk group from one machine is moved to the other,
the Logical Storage Manager may be forced to temporarily remap some
devices.
A base volume device minor number can be set for a disk group with the
minor operand. Volume device numbers for a disk group will be chosen to
have minor numbers starting at this base minor number. On Tru64 UNIX
systems, minor numbers can range up to 1048576, so if it is presumed
that no more than 1000 volumes would ever be created in any one disk
group, then 1048 different ranges of minor numbers are available for
different disk groups. A reasonably sized range should be left at the
end for temporary device number remappings (in the event that two
device numbers still conflict).
If the minor attribute is not specified on the init command line, the
Logical Storage Manager chooses a random number of at least 1000 that
is a multiple of 1000, and yields a usable range of 1000 device
numbers. This default number is chosen such that it does not overlap
within a range of 1000 of any currently imported disk groups, and does
not overlap any currently allocated volume device numbers.
Note
The default policy is likely to ensure that a small number of disk
groups can be merged successfully between a set of machines.
However, in cases where disk groups will be merged automatically
using fail-over mechanisms, the administrator should select ranges
that are known to avoid overlap.
reminor
Changes the base minor number for a disk group, and renumbers all
devices in the disk group to a range starting at that number. If the
device for a volume is open, the old device number will remain in
effect until the system is rebooted or until the disk group is deported
and re-imported. Also, if you close an open volume, you can execute
voldg reminor again to cause the renumbering to take effect without
rebooting or reimporting.
A new device number may also overlap with a temporary renumbering for a
volume device, which will also require a reboot or reimport for the new
device numbering to take effect. A temporary renumbering can happen in
the following situations: when two volumes (for example, volumes in two
different disk groups) share the same permanently assigned device
number, in which case one of the volumes is renumbered temporarily to
use an alternate device number; or when the persistent device number
for a volume was changed, but the active device number could not be
changed to match. The active number may be left unchanged after a
persistent device number change either because the volume device was
open, or because the new number was in use as the active device number
for another volume.
The voldg reminor operation will fail if you try to use a range of
numbers that is currently in use as a persistent (not a temporary)
device number. You can force use of the number range with use of the -f
option. With -f, some device renumberings may not take effect until a
reboot or a re-import (just as with open volumes). Also, if you force
volumes in two disk groups to use the same device number, one of the
volumes will be temporarily renumbered on the next reboot. Which volume
device will be renumbered should be considered random, except that
device numberings in the rootdg disk group take precedence over all
others.
The -f option should be used only when swapping the device number
ranges used by two or more disk groups. To swap the number ranges for
two disk groups, you would use -f when renumbering the first disk group
to use the range of the second disk group. Renumbering the second disk
group to the first range will not require use of -f.
import
Imports a disk group to make the specified disk group available on the
local machine. This will make any configuration information stored with
the disk group accessible, including any disk and volume
configurations. The disk group to import is indicated by the diskgroup
argument, which can be either an administrative disk group name or a
disk group unique ID.
Normally, a disk group will not be imported if some disks in the disk
group cannot be found by the local host. The -f option can be used to
force an import if, for example, one of the disks is currently unusable
or inaccessible.
Note
Take care when using the -f option, since it can cause the same disk
group to be imported twice from disjoint sets of disks, causing the
disk group to become inconsistent.
When a disk group is imported, all disks in the disk group are stamped
with the host's host ID, which is usually the host name. Normally, a
disk group cannot be imported if any of its disks are stamped with a
non-matching host ID. This provides a sanity check in cases where disks
can be accessed from more than one host.
If it is certain that a disk is not in use by another host (such as
because a disk group was not cleanly deported), the -C option can be
used to clear the existing host ID on all disks in the disk group as
part of the import. You can clear a host ID using voldisk clearimport
command.
A new name can be given to the disk group on import using -n newname.
If -n is used with the -t option, the stored name of the disk group
will remain unchanged, but the disk group will be known to the
importing host under the new name; otherwise, the name change will be
permanent.
Normally, an imported disk group will be reimported automatically when
the system is rebooted, if at least some of the disks in the disk group
remain accessible and usable. This can be disabled using the -t option,
which causes the import to persistent only until the system is
rebooted.
As an example of the use of -n and -t, a rootdg disk group from one
host can be imported on a second host, operations can be performed on
the second host (such as making repairs to the root volume), and the
disk group can be given back to the originating host, which can then be
rebooted on the repaired disk group. To do this, identify the disk
group ID for the rootdg disk group with voldisk -s list, and use that
disk group to import that rootdg using -C to clear import locks, -t for
a temporary name, and -n to specify an alternate name (to avoid
collision with the rootdg disk group on the second host). After repair,
deport the disk group using -h (described below) to restore the import
lock from the first host.
deport
Disables access to the specified disk group. You cannot deport a disk
group if any volumes in the disk group are open. When you deport a disk
group, the host ID, which is usually the host name, is cleared on all
disks in the disk group unless you specify a new host ID using the -h
option. This is to automatically prevent reimporting the disk group
when the systems reboots.
A disk group can be renamed on deport by specifying a new disk group
name with -n newname A lock can be assigned to an alternate host by
specifying the host ID (see voldctl(8)) of the alternate host. This
allows the disk group to be auto-imported when the alternate host
reboots. For example, the -n and -h options can be combined to export a
disk group to be used as the rootdg disk group for a new machine.
adddisk
Adds the specified disk(s) to a disk group (rootdg by default). The
disk must not already be part of an imported disk group. The accessname
component to a disk specification argument names a disk access record
(essentially a device address specification) used to access the disk.
If a medianame component is specified, it names the disk media record
used to define the disk within the disk group. If no medianame
component is specified, the disk media record will have the same name
as the disk access record.
Adding a disk to a disk group causes the disk group's configuration to
be copied onto the disk (if the disk has regions for configuration
copies). Also, the disk is stamped with the system's host ID, which is
usually the host name, as defined in the /etc/vol/volboot file.
If the -k option is specified, the disk media name must represent a
disk media record that was previously dissociated from its disk access
record with -k rmdisk; otherwise, a new disk media record will be
created to represent the disk. With the -k option, plexes requiring
recovery will be flagged as stale.
rmdisk
Removes the specified disk(s) from a disk group (rootdg by default).
The last disk cannot be removed from its disk group. It is not possible
to remove the last disk containing a valid disk group configuration or
log copy from its disk group.
Normally, the rmdisk operation will fail if subdisk records point to
the named disk media records. However, if the -k option is specified,
the disk media records will be kept, although in a removed state, and
the subdisk records will still point to them. The subdisks, and any
plexes that refer to them, are unusable until the disk is re-added
using the -k option to the adddisk operation. Any volumes that become
unusable, because all plexes become unusable, will be disabled.
Note
Use extra care with the -k option since this option can disable
active volumes.
list
Lists the contents of disk groups. If no diskgroup arguments are
specified, all disk groups are listed in an abbreviated one-line
format. If diskgroup arguments are specified, a longer format is used
to indicate the status of the disk group, and of the specified disk
group configuration.
If the -q option is specified, no header is printed describing output
fields. This option has no effect with the long formats generated with
diskgroup arguments.
free
Lists free space that can be used for allocating subdisks. If a disk
group is specified, the output is limited to the indicated disk group;
otherwise, space is listed from all disk groups. If disks are specified
by disk media name, the output is restricted to the indicated disks.
A region of free space is identified by disk media name, a physical
device tag, an offset relative to the beginning of the public region
for the media, and a length.
The physical device tag is a reference that indicates which physical
device the disk media is defined on. It appears as a truncated disk
access name. If a particular physical device is split into several
Logical Storage Manager disk objects, the device tag for each Logical
Storage Manager disk object will be the same. Device tags can be
compared to identify space that is on the same or on different physical
disks.
If the -q option is specified, no header is printed describing output
fields. If the -a option is specified, space on spare disks (which is
not really allocatable) is listed in addition to regular free space;
otherwise, space on spare disks is not listed.
spare
Lists spare space that can be used for relocating subdisks during
recovery. If a disk group is specified, the output is limited to the
indicated disk group; otherwise, spare space from all disk groups is
listed. If disks are specified by disk media name, the output is
restricted to the indicated disks.
A region of spare space is identified by disk media name, a physical
device tag, an offset relative to the beginning of the public region
for the media, and a length.
The physical device tag is a reference that indicates which physical
device the disk media is defined on. It appears as a truncated disk
access name.
If the -q option is specified, no header is printed describing output
fields.
flush
Rewrites all disk on-disk structures managed by the Logical Storage
Manager for the named disk groups. This rewrites all disk headers,
configuration copies, and kernel log copies. Also, if any configuration
copies were disabled (for example as a result of I/O failures), this
will rewrite those configuration copies and attempt to enable them.
repldisk
Dissociates the disk access record from the disk media record named by
spare-medianame and reassociates it with the unassociated disk media
record named by unassoc-medianame Both unassoc-medianame and spare-
medianame must be members of the disk group named by the diskgroup
argument (rootdg by default). However, if the -k option is specified,
the disk media records for the spare-medianame will be kept, although
in a removed state.
SEE ALSO
volintro(8), vold(8), voldisk(8), volplex(8), volume(8)
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