voldisk - Defines and manages Logical Storage Manager
disks
/sbin/voldisk [-f] init accessname [attribute...]
/sbin/voldisk [-f] define accessname [attribute...]
/sbin/voldisk offline accessname...
/sbin/voldisk online accessname...
/sbin/voldisk [-a] online
/sbin/voldisk rm accessname...
/sbin/voldisk [-g diskgroup] [-qs] list [disk...]
/sbin/voldisk clearimport accessname...
/sbin/voldisk [-g diskgroup] check disk...
/sbin/voldisk [-g diskgroup] set disk [attribute...]
/sbin/voldisk moddb accessname [attribute...]
Forces an operation that would normally fail. Specifies
all online disks that are not currently in an imported
disk group. Specifies the disk group for the operation.
Suppresses the listing of output field labels. Specifies
the listing of detailed information from the disk header,
including the disk ID, host ID, disk group ID and disk
group name.
The voldisk utility performs basic administrative operations
on disks. Operations include initializing and
replacing disks, as well as taking care of some bookkeeping
necessary for the disk model presented by the Logical
Storage Manager.
The voldisk operations that take an accessname argument
accept only disk access names, which are system-specific
names that relate to disk addresses. On Tru64 UNIX systems,
disk access names are usually of the form dsknp,
where dsk is the device mnemonic for disk devices, n is
the sequence number of the disk, and p is the partition
identifier (in the range a to h). Special devices, such as
internal RAM disks, may use different forms for disk
access names. Disk access names relate directly to device
node names in the /dev/disk directory.
The voldisk operations that take a disk argument can take
disk access names or disk media names (for example,
disk01). For such operations, you can specify a disk group
with -g to distinguish disk media names that are used in
more than one disk group.
Physical disks in the Logical Storage Manager are presumed
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 without affecting correct operation.
The Logical Storage Manager maintains known disk device
address information in a set of disk access records, which
are stored in the rootdg disk group configuration. The
names of these records are based on the disk access name.
These disk access records are normally used solely to
identify which physical disks exist, based on disk IDs
stored on the disks themselves. All voldisk operations
except init and define require specification of defined
disk access records.
Private Region Data Structures [Toc] [Back]
Physical disks contain public regions, which are used for
allocating subdisks. They can also contain private
regions, which are used for storing private Logical Storage
Manager information. Private regions are structured
regions, and are maintained entirely by the Logical Storage
Manager.
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 0 of the
private region. The alternate copy is stored within
the first 256 sectors. If the primary copy is
unreadable or unusable, the Logical Storage Manager
will search 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 contains 0, 1, or 2 disk group configuration
copies, depending on the number specified when the
disk was initialized using the voldisk init operation
(explained later). The default number of
copies is 1. 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 contains 0, 1, or 2 disk group log copies.
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. By default, the
same disks that store one or more configuration
copies also store the same number of log copies.
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 will have to 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 will have to be
reinitialized from scratch.
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, the Logical Storage Manager
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 you clear the host
ID with the clearimport operation.
Disk Types [Toc] [Back]
On Tru64 UNIX systems, three disk types are provided with
the base Logical Storage Manager: nopriv, simple, and
sliced. The default is simple for a disk access name that
specifies a partition (dsknp), and sliced for a disk
access name that specifies the entire disk (dskn).
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 nopriv disks, so they are not
self-identifying, and the Logical Storage Manager cannot
track their movement on a SCSI chain or between controllers.
The nopriv disk type is mainly used for encapsulation of
existing data, or for defining special devices that you
wish to use with the Logical Storage Manager, but that
cannot store private regions (for example, RAM disks).
Initializing a nopriv device with voldisk init creates a
disk access record in the rootdg configuration, but does
not write to the disk. The disk ID for nopriv devices is
stored in the disk access record in the rootdg configuration.
Note
Do not use the type=nopriv attribute to initialize a new
disk with no configuration database. Instead, initialize a
sliced or simple disk and use the nconfig=0 attribute setting.
A simple disk has both a public and a private region,
which are stored on a single disk partition, with the public
region following the private region.
A sliced disk has both a public and a private region,
which are stored on different disk partitions.
The disk label fstype tags for the various LSM disk types
are: LSMpubl for the public region of a sliced disk LSMpriv
for the private region of a sliced disk LSMsimp for a
simple disk (public and private regions are contained
within the same partition) LSMnoprv for a nopriv disk
(maps to an encapsulated disk or disk partition)
Autoconfigured Disks [Toc] [Back]
On Tru64 UNIX systems, the Logical Storage Manager can get
a list of known disk device addresses from the operating
system. Any disks marked for use by LSM are automatically
configured into LSM when vold is started. Disks that are
not configured for LSM use appear as type sliced, with a
status of UNKNOWN.
If LSM disks are not associated with a disk group, you can
remove them from LSM use, if necessary, using voldisk rm.
The next invocation of voldisk list displays those devices
as UNKNOWN, the same as if they had never been in use by
LSM. If you reinitialize a disk for LSM use, the next
invocation of voldisk list reflects its changed status as
an LSM disk. Disks are listed as either in use by LSM or
unknown, but not both.
You can disable and reenable LSM disks using the offline
and online operations. However, the offline state is not
stored persistently unless there is an explicit device
record in the configuration database. If you need to persistently
offline a device at a particular address, you
must convert the address to use an explicit device record.
To do this, remove the autoconfigured device (with voldisk
rm), and use voldisk define to create an explicitly-configured
device.
KEYWORDS AND ATTRIBUTES [Toc] [Back] The behavior of the voldisk utility depends upon the keyword
specified as the first operand. Any attribute
operands override default values assigned for various disk
attributes.
Supported keywords and attributes are: Initializes regions
of a disk for use by the Logical Storage Manager. 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 overrides this and forces initialization of
the disk. You cannot initialize a disk that is a
member of an imported disk group.
The voldisk init operation creates a disk access
record for a disk (if one does not already exist),
and sets its state to online. If the root configuration
is disabled when a disk is initialized, the
disk header is initialized, but the disk is not
added to the permanent list of known disks until
the root configuration is enabled.
You can apply the following disk attributes with
voldisk init: Specifies the disk device access
type, which is a system-specific name identifying a
class of strategies for accessing disks and for
managing private and public regions. For Tru64
UNIX, the valid disk_type names are: nopriv, simple,
and sliced. See the Disk Types section for
details. Specifies that the device will be left in
the offline state, initially. This is used only if
this operation is defining a new disk access
record. For the nopriv device type, this attribute
specifies the usable length of the device, in
512-byte blocks. This is required if there is no
system-defined procedure for determining the disk
length; otherwise, a suitable default is computed.
For the simple or sliced device type, this
attribute specifies the length of the public
region, in 512-byte blocks. If this is not specified,
the length of the public region is computed
from available disk label information. If no such
information is available, a public region length
must be specified. The default public region length
is adjusted to account for the private region, or
for any specified public or private region offsets.
Specifies the offset in blocks from the beginning
of the partition containing the public region to
the beginning of the public region. Use this
attribute if it is necessary to skip over some
region reserved by the operating system. This
attribute does not apply to nopriv disks. For simple
disks, use the privoffset attribute.
This attribute defaults to 0. For sliced disks, an
offset of 16 blocks or greater is a reasonable
value. If the disk is a hardware stripe set, you
can use a different offset to maintain stripe
alignment. If this attribute is specified, the
disk is considered to have volatile contents (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
will inherit that attribute. The volume start operation
interprets volatile plexes as requiring a
complete resynchronization from other plexes in the
same volume.
This attribute applies only to the nopriv device
type. Defines the partition to use for the public
partition. The value of num can be 0-7
(corresponding to partitions a-h). This attribute
applies only to the sliced device type. Defines
the partition to use for the private partition. The
value of num can be 0-7 (corresponding to partitions
a-h). This attribute applies only to the
sliced device type.
You can apply the following attributes with voldisk
init only for the simple or sliced device types:
Specifies the offset in blocks from the beginning
of the partition containing the private region to
the beginning of the private region. The default is
0.
For a simple disk that occupies a partition that
begins at block 0 (for example, when you initialize
the disk specifying the a or c partition), you
should set the privoffset to 16 blocks. For a simple
disk that occupies a partition that does not
begin at block 0 (for example, when you initialize
the disk specifying the b or d partition), the
default of 0 is appropriate.
By default, the private region of a sliced disk is
at the end of the disk (the h partition) and needs
no offset. Therefore the privoffset default of 0
is appropriate. Specifies the length of the private
region in blocks. If this is not specified,
the default of 4096 blocks is used. For a sliced
disk, if no partition information is available, a
private region length must be specified in this
command. Specifies the number of configuration
copies to store on the disk. The number of configuration
copies will be the same as the number of log
regions. The default is 1, but you can set the
attribute to 0 to specify that no configuration
copies be stored on the disk. A setting of 1 is
reasonable for disk groups that contain three or
more disks. This allows either more configuration
records or a smaller reserved private region.
Specifies the size in blocks of the reserved space
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, along with some free space for uses
other than the configuration copies. Specifies the
size in blocks of the reserved space 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. Defines a disk
access record without initializing the disk. The
Logical Storage Manager cannot scan a disk unless a
disk access record is defined for the disk. Thus,
to see what is on a new disk or to move one or more
disks that comprise a valid disk group from one
system to another, you must first use voldisk
define to make the disks accessible. Then you can
use voldisk list to see what is on the disks, or
voldg import to import a disk group that is on
those disks.
Normally, a define operation fails if the specified
disk device is invalid (for example, if the disk is
currently nonexistent). The -f option forces the
definition of an unusable disk. This can be useful
in situations such as preparing the disk device for
use after a reboot. For example, if you intend to
add a new controller and move some existing disks
to the new controller, you may need to define the
new disk device addresses, even though they will
not be usable until you shutdown and reconfigure
your disks.
You can define the following disk attributes with
voldisk define: See the init keyword description
for details. Specifies that the disk be created in
the offline state. See the init keyword description
for details. See the init keyword description
for details. See the init keyword description for
details. Sets the disk ID to the newdiskid value
in the disk access record for the nopriv disk. See
the init keyword description for details. See the
init keyword description for details. See the init
keyword description for details. Declares the disk
devices named by the accessname arguments to be in
the offline state. This disables checking of the
disk when searching for particular disk IDs, or for
the set of disks in a particular disk group. You
cannot place disks offline if they are members of
an imported disk group.
A disk should be placed offline if the disk is not
currently accessible, and if accessing the disk
could have a negative impact on the system. For
example, disk drivers on a few 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. Clears the offline
state for a disk device. This reenables checking of
the disk when searching for disk IDs, or for members
of a disk group. Use this attribute for disks
that are already in the online state, provided that
they are not in imported disk groups. All internal
information for a disk that is already in the
online state is regenerated from the disk's private
region.
The -a places on line all online disks that are not
currently in an imported disk group. Use this
option to force the volume manager to rescan all
disk headers, or to adapt to changes in a disk's
partitioning. Removes the specified disk access
records, by disk access name. Lists detailed disk
information on the specified disks.
If no disk arguments are specified, a one-line summary
is printed for all disk access records known
to the system.
If disk arguments are specified, a full description
of the contents of the disk header and of the table
of contents is printed for each named disk.
If no disk arguments are specified, but a disk
group is specified with -g, voldisk lists only
those disks belonging to the specified disk group.
If the -s option is specified, information from the
disk header is listed, including 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). With -s, the output format
is the same whether or not accessname arguments are
specified.
If the -q option is specified, no header is printed
describing output fields. This option has no effect
with the long formats generated with -s or with
accessname arguments. 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 does not apply to disks that are in
imported disk groups. Validates the usability of
the given disks. A disk is considered usable if the
Logical Storage Manager 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 found to be
unusable, it is detached from its disk group and
all subdisks stored on the disk become invalid
until the physical disk is replaced or the disk
media record is reassigned to a different physical
disk.
Note
Since a nopriv disk does not contain a disk header,
the check keyword might incorrectly report a failed
nopriv disk as okay and usable. Changes some
attributes for a disk. The attributes are either
simple names (used to turn an attribute on or off),
or can be of the form attrname=value, to indicate a
value for a particular attribute.
The set functionality is not currently implemented
for any of the existing disk types. Used with
nconfig=count to change the number of configuration
copies and log copies for the disk device specified
by the accessname argument. See the init keyword
description for details on the nconfig attribute.
The size of the private region is fixed. If there
are two copies of the configuration database on a
disk, each is limited to half the space in the private
region. By decreasing the number of configuration
copies and log copies on a disk, the space
available for the remaining configuration database
on that disk will be increased.
Refer to the Logical Storage Manager manual for
more information about when to use this option.
volintro(8), vold(8), voldg(8), volume(8)
voldisk(8)
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