lvchange(1M)lvchange(1M)NAMElvchange - change LVM logical volume characteristics
SYNOPSIS
availability] autobackup] mirror_consistency] contiguous] schedule]
distributed] mirror_write_cache] permission] relocate] strict]
IO_timeout] lv_path
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 changes certain characteristics of a logical volume. Other
characteristics can be changed with the and commands (see lvextend(1M)
and lvreduce(1M)).
The command-line options specify the type and extent of change. Each
current characteristic for a logical volume remains in effect until
explicitly changed by the corresponding option. All options take
effect immediately, except which takes effect only when new extents are
allocated by the command.
If a logical volume is striped, its scheduling policy is always paral‐
lel and its allocation policy is always strict and noncontiguous; these
attributes cannot be changed with
The command can also be used to change the timeout value for a logical
volume. This can be useful to control how long an IO request will be
retried (for a transient error, like a device timeout), before giving
up and declaring a pending IO to be failed. The default behavior is for
the system to continue to retry an IO for a transient error until the
IO can complete. Thus, the IO will not be returned to the caller until
the IO can complete. By setting a non-zero IO timeout value, this will
set the maximum length of time that the system will retry an IO. If the
IO cannot complete before the length of time specified by the IO time‐
out, then the IO will be returned to the caller with an error. The
actual duration of the IO request may exceed the logical volume's maxi‐
mum IO timeout value when the underlying physical volume(s) have time‐
outs which either exceed the logical volume's timeout value or are not
an integer multiple of the logical volume's timeout value (see
pvchange(1M) for details on how to change the IO timeout value on a
physical volume).
Options and Arguments
The and options are meaningful only if the optional HP MirrorDisk/UX
software has been installed on the system.
recognizes the following options and arguments:
lv_path The block device path name of a logical volume.
Set logical volume availability.
availability can have one of the following values:
Make a logical volume available.
An open of the logical volume will succeed.
Make a logical volume temporarily unavailable.
An open of the logical volume will fail. However,
all current processes that have the logical volume
open remain open.
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 or previ‐
ously set. mirror_consistency can have one of the fol‐
lowing values:
Set mirror consistency recovery on.
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.
contiguous can have one of the following values:
Set a contiguous allocation policy.
Physical extents are allocated in ascending order
without any gap between adjacent extents and all
extents are contained in a single physical volume.
Do not set a contiguous allocation policy.
A nonempty logical volume that has a noncontiguous allo‐
cation policy cannot be changed to a contiguous alloca‐
tion policy unless it happens to meet all the require‐
ments of the contiguous allocation policy. See lvcre‐
ate(1M) for more information about the contiguous alloca‐
tion policy.
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.
Establish a sequential scheduling policy.
Use this value with care, because it leads to per‐
formance loss in most cases.
Change the distributed allocation policy.
distributed can have one of the following values:
Turn on distributed allocation.
Turn off distributed allocation.
Force distributed allocation to be on.
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.
The distributed allocation policy REQUIRES the PVG-strict
allocation policy ( ) to ensure that mirrors of distrib‐
uted extents do not overlap (for maximum availability).
The distributed allocation policy is incompatible with
the striped scheduling policy ( ) and the contiguous
allocation policy ( ).
See lvcreate(1M) for more information on the distributed
allocation policy.
The option will fail if the existing logical volume has
any two consecutive logical extents on the same physical
volume. To override this failure, use the option.
If a logical volume with the distributed allocation pol‐
icy has at least two consecutive logical extents on the
same physical volume, then lvdisplay(1M) will display the
allocation as (vs.
See lvdisplay(1M) for display values.
Set the Mirror Write Cache flag.
This option is allowed only when the logical volume is
not opened. mirror_write_cache can have one of the fol‐
lowing values:
Set Mirror Write Cache on.
Every write to a mirror copy is recorded in the
Mirror Write Cache and written into the Mirror
Consistency Record on the disk if a cache-miss
occurs. This allows LVM to determine whether all
mirror copies are identical, even across system
crashes. When the volume group is activated, the
Mirror Consistency Record is used to perform mir‐
ror consistency recovery.
Set Mirror Write Cache off.
Mirror write does not incur an additional write to
the Mirror Consistency Record on the disk.
Set the access permission.
permission can have one of the following values:
Set the access permission to read-write.
Set the access permission to read-only.
This parameter is valid for volume group version 1.0 only.
For volume group versions 2.0 or higher, it is ignored
and relocation is never 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. This option only makes sense when the
physical volumes of the volume group that owns the speci‐
fied logical volume reside on different physical disks.
strict can have one of the following values:
Set a strict allocation policy.
Mirrors of a logical extent cannot share the same
physical volume.
Set a PVG-strict allocation policy.
Mirrors of a logical extent cannot share the same
physical volume group.
Do not set a strict or a PVG-strict allocation policy.
Mirrors of a logical extent can share the same
physical volume.
When a logical volume is mirrored, the following changes
are not allowed:
· From nonstrict to strict
· From nonstrict to PVG-strict
· From strict to PVG-strict
Set the
IO_timeout for the logical volume to the number of sec‐
onds indicated. This value will be used to determine how
long to wait for IO requests to complete before conclud‐
ing that an IO request cannot be completed. An IO_timeout
value of zero (0) causes the system to use the default
value of "forever". NOTE: The actual duration of the
request may exceed the specified IO_timeout value when
the underlying physical volume(s) have timeouts which
either exceed this IO_timeout value or are not integer
multiples of this value.
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).
LVM shared mode is currently only available in Serviceguard clusters.
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
Change the permission of a logical volume to read-only:
Change the allocation policy of a logical volume to nonstrict:
Turn the mirror write cache off on a logical volume:
Change the IO timeout value of a logical volume to 1 minute (60 sec‐
onds):
WARNINGS
For root, swap or dump logical volumes, the allocation policy is always
contiguous. This attribute cannot be changed with
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 ALSOlvcreate(1M), lvdisplay(1M), lvextend(1M), lvmpud(1M).
lvchange(1M)
