vxdg(ADM)

Synopsis

Description

A diskgroup argument can be either a disk group name or a disk group-ID. A groupname argument is a disk group name, not a disk group-ID. An accessname argument refers to a system-dependent disk access name (also referred to as a disk device name), as stored in the root configuration by the vxdisk utility. If the slice number extension in the disk access record name is not included in the accessname, s0 is assumed by default. If any other slice is required then it should be included in the accessname (as in c0b0t1d0s4). A medianame argument is an administrative name used to define a disk within a disk group.

Supported operations are:

vxdg init

Define 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 pointer to that group in the root configuration, 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, then 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, then the disk media name defaults to accessname. See vxdisk(ADM) 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. If any database locations are listed in the volboot file, then as a special case for initializing rootdg, no disk specifications are allowed. Disks should be initialized and added to the disk group as the first operations after creating rootdg. Some or all disks added to the rootdg disk group should also be added to the volboot bootstrap file (see vxdctl(ADM)).

The nconfig and nlog operands can be used to configure the number of configuration database copies and kernel log copies that are maintained for a disk group. The config-copies and log-copies values are either a decimal number (including 0 or -1) or set to 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 (this is also the default value) signifies that the Volume 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, then each such target is treated similarly to a controller (i.e., 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, then additional copies are spread through the controllers and targets.

Refer to vxdisk(ADM) for more information on configuration and log copies, and for information on how to create them.

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NOTE:If a policy other than all is used, then 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.

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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 Volume 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, then the Volume 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. Minor numbers (in UnixWare) can range up to 131071, so if it is presumed that no more than 1000 volumes would ever be created in any one disk group, then 131 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 no minor operand is specified on the init command line, then the Volume 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.

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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.

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vxdg reminor

Change the base minor number for a disk group, and renumber all devices in the disk group to a range starting at that number. If the device for a volume is open, then 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, then the can execute vxdg-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.

vxdg 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, then 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.

vxdg import

Import 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.

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NOTE:Care must be taken when using the -f flag, since it can cause the same disk group to be imported twice from disjoint sets of disks, causing the disk group to become inconsistent.

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When a disk group is imported, all disks in the disk group are stamped with the host's host ID. 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), then the -C option can be used to clear the existing host ID on all disks in the disk group as part of the import. A host ID can also be cleared using vxdisk clearimport.

A new name can be given to the disk group on import using -n newname. If -n is used with the -t option, then 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 vxdisk -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.

vxdg deport

Disable access to the specified disk group. A disk group cannot be deported if any volumes in the disk group are currently open. When a disk group is deported, the host ID stored on all disks in the disk group will be cleared (unless a new host ID is specified with -h), so the disk group will not be reimported automatically when the system is rebooted.

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 vxdctl(ADM)) 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.

vxdg adddisk

Add 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, then it names the disk media record used to define the disk within the disk group. If no medianame component is specified, then 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, as defined in the volboot file.

If the -k flag is specified, then 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.

vxdg rmdisk

Remove 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 flag is specified, then 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, will be 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.

vxdg list

List the contents of disk groups. If no diskgroup arguments are specified, then all disk groups are listed in an abbreviated one-line format. If diskgroup arguments are specified, then 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, then no header is printed describing output fields. This option has no effect with the long formats generated with diskgroup arguments.

vxdg free

List free space that can be used for allocating subdisks. If a disk group is specified, limit the output to the indicated disk group, otherwise list space from all disk groups. If disks are specified, by disk media name, then restrict the output 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 Volume Manager disk objects, then the device tag for each Volume 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, then no header is printed describing output fields. If the -a option is specified, then 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.

vxdg spare

List spare space that can be used for relocating subdisks during recovery. If a disk group is specified, limit the output to the indicated disk group, otherwise list spare space from all disk groups. If disks are specified, by disk media name, then restrict the output 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, then no header is printed describing output fields.

vxdg flush

Rewrite all disk on-disk structures managed by the Volume 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.

vxdg repldisk

Dissociate the DA record from the DM record named by spare-medianame and reassociate it with the unassociated DM 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 flag is specified, then the disk media records for the spare-medianame will be kept, although in a removed state.

References