vxdisk

NAME

vxdisk - define and manage VERITAS Volume Manager disks

SYNOPSIS

DESCRIPTION

The vxdisk utility performs basic administrative operations on disks. Operations include initializing and replacing disks, as well as taking care of some book-keeping necessary for the disk model presented by VERITAS Volume Manager (VxVM).

accessname refers to the disk access name, while disk represents the disk media name. vxdisk accesses disks based on disk access names, which are system-specific names that relate to disk addresses. Disk access names are in the form c#t#d#, which define a controller number (c#), a SCSI target ID (t#), and a SCSI logical unit number (d#). Disk access names relate directly to device node names in the /dev/dsk and /dev/rdsk directories.

VxVM 3.2 introduced enclosure-based naming as an alternative way of referring to disk access names. If enabled, this scheme maps disk access names relative to their enclosure. For example, disks in the enclosure ENC0 would be assigned access names ENC0_0, ENC0_1 and so on.

Operations that take an accessname argument (see the SYNOPSIS section) accept only disk access names, as defined in the previous paragraph. Operations that take a disk argument can take disk access names or disk media names (for example, disk01). For such operations, a disk group can be specified with -g to disambiguate disk media names that are used in more than one disk group.

Physical disks in VxVM are assumed to be movable, and are usually identified by a unique disk ID stored on the physical disk, rather than by a disk device node. This allows disks to be moved to different SCSI target IDs or to different controllers without affecting correct operation.

VxVM maintains information about disk device addresses as disk access records. Disk access records are used to identify physical disks from disk IDs that are stored on the disks themselves. The name of a disk access record is based on the corresponding disk access name.

Physical disks contain public regions, which are used for allocating subdisks. They can also contain private regions, which are used for storing private VERITAS Volume Manager information. Private regions are configured and maintained entirely by VxVM.

Private regions contain the following structures:

Disk Header

Each private region contains exactly two copies of a disk header, which defines the unique disk ID, disk geometry information, and disk group association information. Two copies are created so that one copy can be lost (due to I/O failures) without causing use of the disk to be lost. The primary copy of the disk header is stored in block zero of the private region. The alternate copy is stored within the first 256 sectors. If the primary copy is unreadable or unusable, VxVM searches the first 256 sectors of the private region for the alternate copy.

Table of Contents

A linked list of blocks, pointed to by the disk header, that define additional structures in the private and public regions. The table of contents blocks define disk group configuration copy locations, log copy locations, and reserved regions carved from the public region. Each link block in the table of contents is replicated at the beginning and end of the private region. If the primary copy of any one link block is unreadable or unusable, the alternate copy of that link is used.

Configuration Copies

A disk normally contains one disk group configuration copy, according to the number specified when the disk was initialized using the vxdisk init operation (explained later). When a disk is added to a disk group, the disk group's persistent configuration records are written to each copy. For disks that are not associated with a disk group, the space allocated for configuration copies is unused. Each disk group requires at least one usable configuration copy. Preferably there should be at least four copies, allocated between at least two disks. This allows one disk to be lost totally, while still preserving sufficient redundancy for recovering from simple read failures.

Disk Group Log Copies

A disk normally contains one disk group log copy. The number of log copies is set to the same as the number of configuration copies for the disk (as explained in the Configuration copies section above). These logs are written by the kernel when certain types of actions are performed: transaction commits, plex detaches resulting from I/O failures, total dirty region log (DRL) failures, the first write to a volume, and volume close. After a crash or a clean reboot, this log information is used to recover the state of a disk group just prior to the crash or reboot. Each disk group requires at least one usable disk group log copy. As with configuration copies, it is preferable to have at least four log copies, allocated between at least two disks.

For a single disk, the disk header and the table of contents blocks are critical data structures. At least one copy of the disk header, and at least one copy of each table of contents block, must be readable and usable, or else the disk itself is unusable and must be reinitialized.

Within disk groups, disk group configuration and log copies are critical data structures. At least one complete configuration copy and log copy must be readable and usable, or the disk group is unusable and must be reinitialized.

All disk group association information is stored in the disk header within private regions. This information consists of a disk group name, disk group unique ID, and a host ID. When the system boots, VxVM scans for disks that are stamped with the system's host ID. Each represented disk group is imported automatically. Disks with a non-matching host ID are not imported automatically, and cannot be used until the host ID is cleared with the clearimport operation.

The behavior of the vxdisk utility depends upon the keyword specified as the first operand.

KEYWORDS

addregion

Adds a new entry to the table of contents in a disk's private region. The new entry defines a region of disk that is relative to the public region, and that is reserved for a particular use. The offset and length operations indicate the location and extent of the region. Currently, the only region type that can be defined is:

reserve

Masks out a region of disk that should be reserved for purposes other than use by VxVM. This could be used, for example, to mask out a boot file system that cannot be used for subdisk allocation, or to mask out a region containing blocks that are used for bad-block or bad-track replacement.

Adding a region fails if a subdisk or region is already allocated over the requested region.

check

Determines the usability of the specified disks. A disk is considered usable if VxVM can write and read back at least one of the disk headers that are stored on the disk. If a disk in a disk group is unusable, VxVM detaches it from its disk group, and all subdisks stored on the disk become invalid. The subdisks remain invalid until the unusable disk is replaced or the disk media record is reassigned to a different physical disk.

For shared disks, VxVM detaches an unusable disk only if the disk group's detach policy is set to global. If the disk group detach policy is local, the disk is not detached. However, if hosts in the cluster do not indicate that a disk is usable, the disk is detached from the entire cluster. See vxedit(1M) for more information on setting disk group detach policies.

clearhost

Clears the stale disk reservation key, as specified by the argument to the -o clearkey option, from a disk.

See the vxdg(1M) manual page for more information about I/O fencing.

clearimport

Clears the host-specific import information stored on the indicated disks, and in the configurations stored on those disks. This command may be necessary in cases where import information stored for a disk group becomes unusable, due to host failures, or due to a disk group being moved from one machine to another.

This operation cannot be applied to disks that are in imported disk groups.

define

Defines a disk access record, but do not initialize it. In order for VxVM to scan a disk, a disk access record must be defined for it. Thus, if you want to see what is on a new disk or you want to move a disk with a valid disk group from one system to another, you must first make it accessible by using vxdisk define. You can use vxdisk list to see what is on the disk, or vxdg\ import to import a disk group that is on the disk.

Attributes can be specified to define the access characteristics of the disk device. The following attributes define the disk type:

type=disk_type

Specifies the access type for the disk device. See the description of the init operation and the DISK TYPES section for more details.

format=format

For auto-configured disks (type=auto), specifies one of the supported formats that is to be used with the disk. See the section Auto-Configured Disks for details.

The various disk types support additional attributes for the define operation. See the DISK TYPES and ATTRIBUTES sections for details.

Normally, a define operation fails if the specified disk device is invalid, such as because no such disk currently exists. The -f option can be used to force definition of an unusable disk. This can be useful if, for example, the disk device could be used after a reboot. For example, if you intend to add a new controller and intend to move some existing disks to the new controller, you may need to define the new disk device addresses, even though they are not usable until you shutdown and reconfigure your disks.

If specified, the -B option initializes the VERITAS Volume Manager private region to begin at block number 2144. This block is designated as the private region offset for a VERITAS Volume Manager root disk. Without this option, the private region is initialized to start at the default block number 128.

destroy

Uninitializes a disk from VxVM by removing the private region and CDS disk labels, which were placed on the disk by an init operation. The -f option forcibly uninitializes a disk.

flush

Rewrite all Cross-Platform Data Sharing (CDS) ID information to the specified disk that has at least one valid VxVM ID block. Unlike the vxdg flush command, the disk is brought online if required.

The -f option may be specified to forcibly rewrite the AIX coexistence label and VxVM ID block. By default, these are not overwritten.

getctlr

Returns the name of the controller associated with a given disk access name.

init

Initializes regions of a disk used by VxVM. This involves installing a disk header and writing an empty configuration on the disk. The accessname operand identifies the disk. Normally, this command fails if the disk already contains an apparently valid disk header. The -f option can be used to override this and to force initialization of the disk. A disk that is a member of an imported disk group cannot be initialized.

The vxdisk\ init operation creates a disk access record for a disk (if one does not already exist), and sets its state to online. Disks can be initialized when vxconfigd is in its disabled state, in which case the disk header is initialized, but the disk is not added to the list of known disks until vxconfigd is re-enabled.

Any attribute operands override default values assigned for various disk attributes. Some attributes that can be set are:

type=disk_type

Specifies the access type for the disk device. This type identifies the class of strategies that can be used to access the disk, and to manage its private and public regions.

For example, a disk type can indicate a networked disk or a volatile RAM disk that does not require the storage of any private data.

See the description of the init operation and the DISK TYPES section for more details.

format=format

For auto-configured disks (type=auto), specifies one of the supported formats that is to be used with the disk. See the section Auto-Configured Disks for details.

The various disk types support additional attributes for the init operation. See the DISK TYPES and ATTRIBUTES sections for details.

If specified, the -B option initializes the VERITAS Volume Manager private region to begin at block number 2144. This block is designated as the private region offset for a VERITAS Volume Manager root disk. Without this option, the private region is initialized to start at the default block number 128.

list

Lists path type and states along with the detailed information on the specified disks. The state is listed as enabled or disabled.

If one or more disk arguments are specified, a full description of the contents of the disk header and of the table of contents for each named disk is displayed.

If no disk arguments are specified, a one-line summary for all disk access records known to the system is displayed.

If no disk arguments are specified, but a disk group is specified with -g, information is displayed about only those disks that have been added to the specified disk group.

The -b option can be used to display length and offset values in 512-byte units, regardless of platform. If this option is not specified, values are displayed in units of sectors, the size of which can vary between different platforms.

If the -s option is specified, important information from the disk header is displayed. With the -s option, the output format is the same whether or not accessname arguments are specified. The information printed with -s includes the disk ID, the host ID (if the disk is or was imported), and the disk group ID and disk group name (if the disk is a member of a disk group).

If the -q option is specified, no header is printed that describes output fields. This option has no effect with the long formats that are generated for the -s option or for accessname arguments.

When -o alldgs is specified without the -s and -g options, a one line summary shows all associations between disks and disk groups. The disk group column shows imported disk groups as normal and shows all other disk groups in parentheses.

Auto-configured disks are shown with their type (auto) qualified by their format. For example, auto:cdsdisk indicates an auto-configured disk that is formatted as a CDS disk. See the Auto-Configured Disks section for more details.

You can use the -o listreserve option to discover if I/O fencing has been enabled for a disk group. If I/O fencing is enabled, the command also displays the current reservations and registered keys for the disks in the disk group. See the vxdg(1M) manual page for more information about I/O fencing.

offline

Declares the disk devices named by the accessname arguments to be in the offline state. This disables checking of the disk in searching for particular disk IDs, or for the set of disks in a particular disk group. This operation cannot be applied to disks that are members of an imported disk group.

Take a disk offline if the disk is not currently accessible, and if accessing the disk has a negative impact on the system. For example, disk drivers on a some operating systems can cause system panics or hangs if an attempt is made to access disks that are not accessible. In other operating systems, attempts to access inaccessible drives may take several seconds or minutes before returning a failure.

online

Clears the offline state for a disk device. This re-enables checking of the disk when searching for disk IDs, or for members of a disk group. This can be used for disks that are already in the online state, provided that they are not in imported disk groups. All internal information for an already online state disk is regenerated from the disk's private region.

If -a is specified, re-online all online disks that are not currently in an imported disk group. This can be used to force VxVM to re-scan all disk headers.

path

Lists the disk access name, disk media name, disk group and state that are associated with each subpath on the system. If a disk group is specified using the -g option, only subpaths that are associated with that disk group are listed.

resize

Resizes a virtual disk device with a SCSI interface presented by a smart switch, smart array or RAID controller. Following a resize operation to increase the length that is defined for a device, additional disk space on the device is available for allocation. You can optionally specify the new size by using the length attribute.

If a disk media name rather than a disk access name is specified, the disk group must also be specified using the -g option.

Caution: Do not perform this operation when replacing a physical disk with a disk of a different size as data is not preserved.

Caution: Before reducing the size of a device, any volumes on the device should first be reduced in size or moved off the device. By default, the resize fails if any subdisks would be disabled as a result of their being removed in whole or in part during a shrink operation.

If the device that is being resized has the only valid configuration copy for a disk group, the -f option may be specified to forcibly resize the device.

Caution: Resizing a device that contains the only valid configuration copy for a disk group can result in data loss if a system crash occurs during the resize.

Caution: Resizing a virtual disk device is a non-transactional operation outside the control of VxVM. This means that the resize command may have to be re-issued following a system crash. In addition, a system crash may leave the private region on the device in an unusable state. If this occurs, the disk must be reinitialized, reattached to the disk group, and its data resynchronized or recovered from a backup.

rm

Removes the specified disk access records, by disk access name.

rmregion

Frees a region of space that is allocated in the private or public region for a particular use. Space that is freed from the public region becomes usable for subdisk creation. The arguments to rmregion must match the arguments used when adding the region with vxdisk addregion except for the optional length argument which can be excluded for the remove.

scandisks

Initiates rescanning of devices in the OS device tree by VxVM. If necessary, DMP reconfiguration is triggered. This allows VxVM to configure and multipath disks dynamically.

The following scandisks operations are also supported:

scandisks new

Discovers new disks (that is, disks not known to VxVM).

scandisks fabric

Discovers fabric devices.

scandisks [!]device=device_list

Discovers and configures the devices that are specified as a comma-separated list. If a ! is prepended to device, all devices except those listed are discovered.

scandisks [!]ctlr=controller_list

Discovers devices that are connected to the logical controllers specified as a comma-separated list. If a ! is prepended to device, all devices are discovered except those that are connected to the specified controllers.

scandisks [!]pctlr=physical_controller_list

Discovers devices that are connected to the physical controllers specified as a list of items separated by + characters. If a ! is prepended to device, all devices are discovered except those that are connected to the specified physical controllers.

A list of physical controllers can be obtained by running the vxdmpadm listctlr all command.

Only one scandisk operation may be specified at a time. For example, a command such as vxdisk scandisks new fabric results in an error.

set

Changes some set of attributes for a disk. The attributes are either simple names (used to turn on an on/off attribute), or can be of the form attrname=value, to indicate a value for a particular attribute.

HARDWARE-SPECIFIC NOTE

Some environments provide guidelines to optimize VxVM's interaction with intelligent storage systems. If these guidelines are present, VxVM follows them when initializing disks, creating volumes or allocating space for volumes. These rules cannot be overridden.

DISK TYPES

Three disk types are supported for use with VxVM: simple, nopriv, auto with format set to hpdisk, cdsdisk or none.

The default type is auto with format set to cdsdisk for disks other than EFI disks. If required, this default can be overridden in the /etc/default/vxdisk file. If an EFI disk is initialized, the default format is hpdisk.

NOPRIV DISKS

The simplest disk type is nopriv, which defines a disk that has no private region, and that consists only of space for allocating subdisks. Configuration and log copies cannot be stored on such disks, and such disks do not support reserved regions defined with vxdisk\ addregion. Because nopriv disks are not self identifying, VxVM cannot track the movement of such disks on a SCSI chain or between controllers.

nopriv devices are most useful for defining special devices (such as volatile RAM disks) that you wish to use with VxVM, but that cannot store private regions. A RAM disk cannot store a meaningful private region, because data written to a RAM disk may not survive a reboot.

Initializing a nopriv device with vxdisk\ init creates a disk access record internally to VxVM's configuration, but no information is written to disk. The disk ID for nopriv devices is stored in the private structure of the disk access record.

Attributes that can be used with the define operation for nopriv disks are diskid, publen, puboffset and volatile.

Attributes that can be used with the init operation for nopriv disks are publen, puboffset and volatile.

SIMPLE DISKS

The simple type presumes that the public and private regions are stored on the same disk, with the public region following the private region.

Attributes that can be defined with vxdisk define for simple disks are listed in the ATTRIBUTES section.

AUTO-CONFIGURED DISKS

On some systems, VxVM can ask the operating system for a list of known disk device addresses. On such systems, some device addresses are auto-configured when vxconfigd is started.

From release 4.0 of VxVM, auto-configured disks are of type auto that can take one of the following formats:

cdsdisk

The disk is formatted as a CDS disk that is suitable for moving between different operating systems. This is the default format for most disks, but it is not suitable for boot disks or EFI disks.

hpdisk

The disk is formatted for use with VxVM on HP-UX. This format can be applied to disks that can be used to boot the system. If the disk is not initialized as a boot disk, space is reserved on the disk to allow it to be converted to cdsdisk format if required.

none

The disk is an unformatted auto-configured disk.

Auto-configured devices can be removed, if necessary, by using the vxdisk\ rm command. When removed, explicitly defined devices can be defined to override any auto-configured devices. When the system reboots, no auto-configured disk devices are added to the VxVM configuration if that meant that they would share a disk with an explicitly configured disk device.

Auto-configured devices can be disabled and re-enabled using the offline and online operations. However, the offline state is not stored persistently. If you need to persistently offline a device at a particular address, convert the address to use an explicit device record. To do this, remove the auto-configured device, and use vxdisk define to create an explicitly configured device.

Attributes that may be defined for auto-configured disks are listed in the ATTRIBUTES section.

The default format for auto-configured disks may be overridden by a suitable entry in the /etc/default/vxdisk file. See the DEFAULTS FILE section for details. A value specified on the command line takes precedence over both the value in the defaults file and the inbuilt value.

ATTRIBUTES

configlen=length

The size to reserve for each copy of the configuration stored on the disk. The default size is based on the size of the private area and the number of configuration copies requested, and leaves some space free for uses other than the configuration copies.

diskid=newdiskid

For a nopriv disk, this defines the value newdiskid for the disk ID in the disk access record.

loglen=length

The size to reserve in the private region for each log region. This size limits the number of kernel-initiated detach operations that can be logged against the disk group. The default is about 15% of the size of the configuration copies. It is advised that the log sizes be kept as 15% of the configuration copy size.

nconfig=count

The number of configuration copies to store on the disk. This defaults to 1. Setting this value to 0 indicates that no configurations are to be stored on the disk.

VxVM automatically enables and disables the configuration copy. It maintains a level of redundancy in configuration copies that allows the configuration to be recovered from the loss of multiple disks.

See the description of the nconfig parameter on the vxdg(1M) manual page for more information.

nlogs=count

The number of log regions to allocate on the disk. Log regions are used for storing any plex detaches that happen within the disk group. This number defaults to 1.

VxVM automatically enables and disables the configuration copy. It maintains a level of redundancy in configuration copies that allows the configuration to be recovered from the loss of multiple disks.

See the description of the nlog parameter on the vxdg(1M) manual page for more information.

offline

If specified, creates disk in the offline state for the define operation, or leaves the device in the offline state initially for the init operation. This attribute is used only if a new disk access record is being defined.

privlen=length

The length of the private region. If this is not specified, then a default is chosen. For the simple and cdsdisk types, the default size is 2048 blocks. The maximum possible size of the private region is 524288 blocks.

The default value of privlen may also be overridden by a suitable entry in the /etc/default/vxdisk file. See the DEFAULTS FILE section for details. A value specified on the command line takes precedence over both the value in the defaults file and the inbuilt value.

publen=length or len=length

For disk types other than nopriv, the length of the public region. If not specified, the length of the public region is computed from available system-specific disk size information. If no such information is available, a public region length must be specified in this command. The default public region length is adjusted to account for the private region, or for any specified public or private region offsets.

For nopriv disks, the usable length of the device. This is required if there is no system-defined procedure for determining the disk length; otherwise, a suitable default is computed.

puboffset=offset or offset=offset

For nopriv disks, the offset within the device for the start of the usable region. The default value of this offset defaults to 1. This can be changed if it is necessary to skip over some region that is reserved for use by the operating system. If an offset is specified, the default disk length is adjusted accordingly.

volatile

For a nopriv disk, this marks the contents of the disk as being volatile (that is, the disk contents are not expected to remain consistent across a system reboot). Subdisks and plexes defined on disks with the volatile attribute inherit that attribute. The vxvol\ start operation interprets volatile plexes as requiring complete revival from other plexes in the same volume.

DEFAULTS FILE

The /etc/default/vxdisk file can be used to set the default values of the format and privlen attributes for the vxdisk and vxdisksetup commands. Values in this file override inbuilt values, and may themselves be overridden by values specified on the command line.

The following attributes may be specified in the defaults file:

format=format

Defines the default format for auto type disks. Supported values of format are hpdisk and cdsdisk. The setting of this attribute is considered for the define and init operations.

privlen=length

Defines the default length for the private region. See the ATTRIBUTES section for a full definition. The setting of this attribute is considered for the init operation only.

The attributes and their values may be defined in any order in the file, the attribute keyword must start in the first column, and no white-space characters are allowed around the = character. If an attribute is defined multiple times, only the final occurrence in the file is used. Commands silently ignore any definition line that has an invalid format.

EXAMPLES

This example sets the powerfail timeout on disk01.

The set functionality is currently unimplemented for any of the existing disk types.

Use the getctlr keyword to return the controller associated with a disk that is specified by its enclosure-based disk access name.

FILES

/etc/default/vxdisk

Defaults file used by the vxdisk and vxdisksetup utilities.

NOTES

Auto-configured disks of type auto with the cdsdisk format cannot be used as boot, root, or swap disks. Such disks can also only be created and used in a disk group that has a version number greater than or equal to 110.

To ensure that the VTOC and disk format are in agreement, it is recommended that you use the vxdisksetup -i command to initialize disks in preference to the vxdisk init command.

SEE ALSO

pfto (7), vxcdsconvert (1M), vxconfigd (1M), vxdg (1M), vxdisksetup (1M), vxedit (1M), vxintro (1M), vxvol (1M)