PVChange - Change Physical Volume Attributes
The pvchange command is a powerful utility in Linux's
Logical Volume Manager (LVM) suite, designed to modify the
attributes of a physical volume (PV). This tool allows
administrators to control how a physical disk or partition is used
within an LVM setup, offering flexibility in managing storage
resources.
Understanding PVChange Options
pvchange provides several key options to alter the
state and behavior of a physical volume:
Changing PV Allocatable Status
One of the primary uses of pvchange is to control
whether a physical volume can be used for allocating logical
volumes. This is managed using the -x or
--allocatable flag.
-
To set a physical volume as
not allocatable (effectively taking it out of the
pool for new allocations):
pvchange -x n /dev/sdX -
To set a physical volume as allocatable (making
it available for new allocations):
pvchange -x y /dev/sdX
Modifying PV Metadata
pvchange also allows for the manipulation of metadata
associated with a physical volume, which is crucial for LVM's
internal tracking and management.
-
To change the metadata ignore flag of a physical
volume. This flag can be used to prevent LVM from considering the
metadata on a PV, which can be useful in certain advanced
scenarios or during migration processes:
pvchange --metadataignore y /dev/sdX -
To specify the metadata type. For instance,
enabling 64-bit metadata, which is essential for larger storage
configurations and newer LVM versions:
pvchange --metadata-type lvm2 /dev/sdX
Practical Applications and Considerations
Using pvchange is a common practice when performing
maintenance on LVM storage. For example, before removing a disk from
a system or resizing an LVM volume group, you would typically mark
the relevant physical volumes as non-allocatable to ensure no new
data is written to them. This prevents data corruption and ensures a
smooth transition.
It's important to note that while
pvchange -x n prevents new allocations, it does not
affect existing logical volumes that are already using the physical
volume. For complete removal or deactivation of a physical volume,
you would typically use commands like pvremove after
ensuring all logical volumes on it have been moved or removed.