lvchange(1M) lvchange(1M)
NAME
lvchange - change LVM logical volume characteristics
SYNOPSIS
availability] autobackup] mirror_consistency] contiguous] schedule] distributed] mirror_write_cache] permission] relocate] strict] IO_time-
out] 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 lvex-
tend(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 parallel 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 timeout, 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 maximum IO timeout value when the underlying physical
volume(s) have timeouts which either exceed the logical volume's timeout value or are not an integer multiple of the logical volume's time-
out 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 previously set. mirror_consistency can have one of the following 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 mirror 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 con-
tained in a single physical volume.
Do not set a contiguous allocation policy.
A nonempty logical volume that has a noncontiguous allocation policy cannot be changed to a contiguous allocation policy
unless it happens to meet all the requirements of the contiguous allocation policy. See lvcreate(1M) for more information
about the contiguous allocation 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 values:
Establish a parallel scheduling policy.
Establish a sequential scheduling policy.
Use this value with care, because it leads to performance 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 vol-
ume. 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 distributed 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 policy 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 following 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 mirror consis-
tency 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 compatibility with
prior HP-UX releases. The relocate flag can have one of the following values:
This release does not provide the LVM bad block relocation feature;
but for compatibility reasons, the value is maintained 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 relocation feature, bad
blocks may be relocated depending upon the value of this flag. Although no new relocations will be done, any bad
block relocations 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 specified 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:
o From nonstrict to strict
o From nonstrict to PVG-strict
o From strict to PVG-strict
Set the
IO_timeout for the logical volume to the number of seconds indicated. This value will be used to determine how long to wait
for IO requests to complete before concluding 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_time-
out 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 seconds):
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 logi-
cal volume with mirror consistency recovery turned off are:
o data not needed after a crash, such as swap or other raw scratch data, or
o 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 ALSO
lvcreate(1M), lvdisplay(1M), lvextend(1M), lvmpud(1M).
lvchange(1M)