lvcreate(1M)lvcreate(1M)NAMElvcreate - create logical volume in LVM volume group
SYNOPSIS
autobackup] mirror_consistency] contiguous] schedule] distributed]
stripes stripe_size]] le_number | lv_size] mirror_copies] mir‐
ror_write_cache] lv_name] permission] relocate] strict] vg_name
Remarks
Mirrored disk operations require the installation of the optional HP
MirrorDisk/UX software, which is not included in the standard HP-UX
operating system.
DESCRIPTION
The command creates a new logical volume within the volume group speci‐
fied by vg_name. The total number of logical volumes that can be cre‐
ated depends on the version of the volume group. Use the command to
find the maximum number of logical volumes for each volume group ver‐
sion. See lvm(7) for more information.
If you specify the option, a new logical volume is created with that
name. Otherwise, a system-generated name of the form is created. For
a logical volume created within a volume group version 1.0, N is the
decimal equivalent of the two least significant bytes of the minor num‐
ber of the new logical volume and the range for N is 1 to 255. For a
logical volume created within a volume group version 2.0, N is the dec‐
imal equivalent of the least significant 12 bits of the logical volumes
minor number, and the range for N is 1 to 511. For a logical volume
created within a volume group version 2.1, N is the decimal equivalent
of the least significant 12 bits of the logical volumes minor number,
and the range for N is 1 to 2047 (see lvm(7)).
Two device files are created in vg_name: a block device file named
lv_name or and a character (raw) device file named or
If you omit the and options, the logical volume is created with zero
length. This permits you to choose its physical volume location when
you allocate logical extents with the command (see lvextend(1M)). If
you specify or the location is determined automatically.
The default settings provide the most commonly used characteristics.
Use the options to tailor the logical volume to the requirements of the
system. Once a logical volume is created, some of its characteristics
can be changed with the and commands (see lvchange(1M), lvextend(1M),
and lvreduce(1M)).
Options and Arguments
The and options are only meaningful if the optional HP MirrorDisk/UX
software has been installed on the system.
recognizes the following options and arguments:
vg_name The path name of a volume group.
Set automatic backup for this invocation of this command.
autobackup can have one of the following values:
Automatically back up configuration changes made to the
logical volume.
This is the default.
After this command executes, the command (see
vgcfgbackup(1M)) is executed for the volume group
to which the logical volume belongs.
Do not back up configuration changes this time.
Set mirror consistency recovery.
This option is effective only when is specified. It is
ignored for mirror_consistency can have one of the fol‐
lowing values:
Set mirror consistency recovery on.
This is the default.
LVM achieves mirror consistency during volume
group activation by going through all logical
extents and copying data from a nonstale copy to
the other mirror copies.
Set mirror consistency recovery off.
LVM does not perform mirror consistency recovery
on this logical volume when the volume group is
activated following a system crash. This setting
should only be used on logical volumes that do not
require mirror consistency recovery or where mir‐
ror consistency recovery is performed by another
subsystem; for example swap. See the section for
more details.
Set the contiguous allocation policy.
A contiguous logical volume has three characteristics:
· Physical extents are allocated in ascending order,
· No gap is allowed between physical extents within a
mirror copy,
· Physical extents of any mirror copy all reside on a
single physical volume.
Use the strict and contiguous options together to form
various combined allocation policies on a logical volume.
For example, defines a logical volume such that each mir‐
ror copy is contiguous, yet mirror copies of a logical
extent cannot share the same physical volume.
contiguous can have one of the following values:
Set a contiguous allocation policy.
Do not set a contiguous allocation policy.
This is the default.
The enforcement of a contiguous allocation policy via the
option is not supported on a striped logical volume.
Set the scheduling policy when a logical extent
with more than one mirror is written. (The scheduling
policy of a striped logical volume is striped and cannot
be changed.) schedule can have one of the following val‐
ues:
Establish a parallel scheduling policy.
This is the default.
Establish a sequential scheduling policy.
Use this value with care, because it leads to per‐
formance loss in most cases.
Set the distributed allocation policy.
distributed can have one of the following values:
Turn on distributed allocation.
Turn off distributed allocation.
This is the default.
When the distributed allocation policy is turned on, only
one free extent is allocated from the first available
physical volume. The next free extent is allocated from
the next available physical volume. Allocation of free
extents proceeds in round-robin order on the list of
available physical volumes.
When the distributed allocation policy is turned off, all
available free extents are allocated from each available
physical volume before proceeding to the next available
physical volume. This is the default.
The distributed allocation policy REQUIRES the PVG-strict
allocation policy to ensure that mirrors of distributed
extents do not overlap (for maximum availability).
lvcreate(1M) will obtain the list of available physical
volumes from See vgextend(1M) for more information on
physical volume groups and
When a logical volume with distributed extents is mir‐
rored, the resulting layout is commonly referred to as
EXTENT-BASED MIRRORED STRIPES.
Note that EXTENT-BASED MIRRORED STRIPES can be created
without the distributed allocation policy by adding one
extent at a time to the desired physical volumes through
lvextend(1M).
The distributed allocation policy is incompatible with
the striped scheduling policy and the contiguous alloca‐
tion policy
The lvchange(1M) command can be used to assign the dis‐
tributed allocation policy to an existing logical volume.
See lvdisplay(1M) for display values.
See
Set the number of disks to stripe across.
stripes must be at least 2 and no greater than a volume
group version-dependent maximum; use the command to
determine the maximum supported stripes for the volume
group version.
If is provided and is not, the stripe size is set to 8
kilobytes.
Set the size in kilobytes of the stripe.
stripe_size should be a power of 2. stripe_size must be
at least 4 and no greater than a volume group version-
dependent maximum; use the command to determine the maxi‐
mum supported stripe_size for the volume group version.
If is provided and is not, the command will fail and
return an error. Stripe size should be a value less than
or equal to physical extent size and must be specified
with the option.
Allocate space to the logical volume,
specified in logical extents.
le_number must be at least 1 and no greater than a volume
group version-dependent maximum; use the command to
determine the maximum number of logical extents for the
volume group version.
The default is described above.
Either or can be specified, but not both.
Allocate space to the logical volume,
specified in megabytes. lv_size must be at least 1 and
no greater than a volume group version-dependent maximum;
use the command to determine the maximum size for the
volume group version.
lv_size is rounded up to the nearest multiple of the log‐
ical extent size, equivalent to the physical extent size
defined for the volume group by the command (see vgcre‐
ate(1M)). The default is described above.
Either the or the option can be specified, but not both.
Set the number of mirror copies allocated for each logical
extent.
A mirror copy contains the same data as the original.
mirror_copies must be at least 1 and no greater than a
volume group version-dependent maximum; use the command
to determine the maximum number of mirror copies for the
volume group version. The default value is 0 (no mirror
copies).
Set the Mirror Write Cache flag.
mirror_write_cache can have one of the following values:
Set Mirror Write Cache on.
This is the default.
Every write to a mirror copy is recorded in the
Mirror Write Cache. The Mirror Consistency Record
in the Volume Group Reserved Area on the disk is
updated whenever there is a write to a logical
track group that is not already recorded in the
cache. This allows LVM to determine whether all
the mirror copies are identical, even across sys‐
tem crashes. When the volume group is activated,
the Mirror Consistency Record is used to perform
mirror consistency recovery.
Set Mirror Write Cache to off.
Mirror write does not incur an additional write to
the Mirror Consistency Record.
Set the name of the new logical volume to
lv_name, where lv_name is a simple file name, not a path
name. The default is described above.
Set the access permission.
permission can have one of the following values:
Set the access permission to read-write.
This is the default.
Set the access permission to read-only.
This parameter is valid for creating a logical volume within
volume groups version 1.0 only. For volume groups ver‐
sions 2.0 or higher, it is ignored and relocation is not
supported.
Set the logical volume bad block relocation policy. This
is an obsolete flag available only to provide compatibil‐
ity with prior HP-UX releases. The relocate flag can
have one of the following values:
This release does not provide the LVM bad block reloca‐
tion feature;
but for compatibility reasons, the value is main‐
tained as a logical volume attribute. Displaying
the logical volume attributes will show the value
of the flag selected. However, regardless of the
selection, no new relocations will be done.
If the volume group is activated on a different
HP-UX release that provides the bad block reloca‐
tion feature, bad blocks may be relocated depend‐
ing upon the value of this flag. Although no new
relocations will be done, any bad block reloca‐
tions present on a logical volume (activated on
HP-UX releases that provided this feature) will be
honored when the volume group is activated on this
HP-UX release.
is the default value of this flag.
Set the strict allocation policy.
Mirror copies of a logical extent can be allocated to
share or not share the same physical volume or physical
volume group. strict can have one of the following val‐
ues:
Set a strict allocation policy.
Mirrors of a logical extent cannot share the same
physical volume. This is the default.
Set a PVG-strict allocation policy.
Mirrors of a logical extent cannot share the same
physical volume group. A PVG-strict allocation
policy cannot be set on a logical volume in a vol‐
ume group that does not have a physical volume
group defined.
Do not set a strict or PVG-strict allocation policy.
Mirrors of a logical extent can share the same
physical volume.
Striped Logical Volume Considerations
Striped and mirrored logical volumes are supported. A logical volume
striped across stripes physical volumes is allocated in sets of stripes
logical extents. A set corresponds to stripes physical extents if the
volume is not mirrored or to stripes * (mirror_copies + 1) physical
extents if the volume is mirrored. stripes is the number of physical
volumes the logical volume is striped across. It is set with the
option stripes. mirror_copies is the number of mirror copies allocated
for each logical extent. It is set with the option. The user data is
striped across stripes physical extents of the set, and each of these
extents is mirrored on mirror_copies other physical extents of the same
set. Striped logical volumes are only allocated using the strict or
PVG-strict allocation policies. Each physical extent of a given set is
allocated on a different physical volume in the volume group.
The total number of physical extents of a striped logical volume is
always a multiple of stripes (or stripes * (mirror_copies + 1) if the
volume is mirrored).
A minimum of stripes (or stripes * (mirror_copies + 1) if the volume is
mirrored) physical volumes with adequate free space and meeting the
allocation policy is needed to allocate a striped logical volume.
Shared Volume Group Considerations
For volume group version 1.0 and 2.0, cannot be used if the volume
group is activated in shared mode. For volume groups version 2.1 (or
higher), can be performed when activated in either shared, exclusive,
or standalone mode.
Note that the daemon must be running on all the nodes sharing a volume
group activated in shared mode. See lvmpud(1M).
When is issued, it creates the logical volume device special files on
all the nodes sharing the volume group. The device special files are
created with the same name on the nodes sharing the volume group.
When a node wants to share the volume group, the user must first exe‐
cute a if logical volumes were created at the time the volume group was
not activated on that node.
The logical volumes device special files should have the same name on
all the nodes sharing the volume group.
If PVG-strict allocation policy is set, the file used is the one on the
system where the command is issued.
LVM shared mode is currently only available in Serviceguard cluster.
EXTERNAL INFLUENCES
Environment Variables
determines the language in which messages are displayed.
If 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)).
EXAMPLES
Create a logical volume in volume group
Create a logical volume in volume group with non-strict allocation pol‐
icy:
Create a logical volume of size 100 MB in volume group
Create a logical volume of size 90 MB striped across 3 disks with a
stripe size of 64 KB:
Create a logical volume of size 90 MB striped across 3 disks with one
mirror copy and a stripe size of 64 KB:
Distributed Allocation Policy
This example shows how the option can be used to create EXTENT-BASED
MIRRORED STRIPES.
Assume that volume group has two physical volume groups: and
Assume that each physical volume group has 2 physical volumes.
Assume that the first physical volume in each pvg has 3 extents free
and the second physical volume in each pvg has 2 extents free.
The following command creates a logical volume in vgtest with EXTENT-
BASED MIRRORED STRIPES:
The distributed allocation proceeds as follows:
· A free extent is allocated from the 1st pvol in pvg1.
· A free extent is allocated from the 2nd pvol in pvg1.
· A free extent is allocated from the 1st pvol in pvg1.
· A free extent is allocated from the 2nd pvol in pvg1.
· A free extent is allocated from the 1st pvol in pvg1.
· Mirrors for the five extents are then allocated from the free
extents in pvg2 in a similar manner.
WARNINGS
The root, swap, and dump logical volumes (see lvlnboot(1M)) must be
created with contiguous allocation policy.
The creation of striped and mirrored logical volume(s) may prevent the
import and activation of the volume group on an earlier HP-UX release.
See lvcreate(1M) on the earlier release to see if it explicitly states
that striping and mirroring is supported. If the striped and mirrored
logical volumes of the volume group are removed or un-mirrored, the
volume group becomes again compatible with the older HP-UX releases.
By setting mirror consistency recovery off, crash recovery time will be
reduced. After a system crash the mirrored logical volume will be
available, but there may not be consistent data across each mirror
copy. The only types of data that can safely be put on a mirrored log‐
ical volume with mirror consistency recovery turned off are:
· data not needed after a crash, such as swap or other raw scratch
data, or
· data that an application itself will automatically reconstruct; for
example, a raw logical volume for which a database keeps a log of
incomplete transactions.
SEE ALSOlvchange(1M), lvdisplay(1M), lvextend(1M), lvmadm(1M), lvmpud(1M),
lvreduce(1M), pvchange(1M), intro(7), lvm(7).
lvcreate(1M)
