lvconvert
The lvconvert command is used in Linux Logical Volume Manager (LVM) to modify the properties of an existing logical volume (LV). It allows you to convert a logical volume to a different type or configuration. For example, you can convert a regular volume into a thinly provisioned volume, a mirrored volume, or even add or remove mirrors.
Syntax
lvconvert [options] <lvname>Where:
<lvname>: The name of the logical volume you want to modify (e.g.,/dev/vgname/lvname).
Common Use Cases
Here are some common ways to use lvconvert:
1. Convert to a Mirrored Logical Volume
If you have a non-mirrored logical volume (LV) and want to convert it to a mirrored LV, you can use the following syntax. The --mirror option allows you to create a mirrored volume.
Example: Convert to a Mirrored Volume (RAID 1)
sudo lvconvert --mirror 1 /dev/vgname/lvname--mirror 1: This option specifies that one mirror copy should be created. You need at least two physical volumes in the volume group for mirroring.This command will add a mirror to the logical volume, giving you redundancy (RAID 1).
2. Convert to a Thin-Provisioned Logical Volume
You can convert a standard logical volume to a thin-provisioned volume (thin provisioning allows you to allocate space as needed, rather than reserving it all upfront).
Example: Convert to Thin Volume
sudo lvconvert --type thin /dev/vgname/lvname--type thin: Specifies that the logical volume should be converted to a thin-provisioned volume.This command will allow you to make better use of space by allocating space only when the data is actually written to the volume.
3. Convert Thin-Provisioned to Regular Volume
If you no longer need the thin provisioning and want to convert it back to a regular volume, you can use lvconvert with the --type option set to default.
Example: Convert Thin Volume to Regular Volume
sudo lvconvert --type default /dev/vgname/lvname--type default: Converts the thin-provisioned LV back to a standard LV, with space allocated upfront.
4. Convert to a Snapshot Volume
You can convert a regular logical volume into a snapshot logical volume, which is a read-only copy of the original logical volume that can be used for backups or testing purposes.
Example: Convert to Snapshot
sudo lvconvert --snapshot /dev/vgname/lvname--snapshot: Converts the logical volume into a snapshot, which is a point-in-time copy of the LV.
5. Add Mirrors to an Existing Logical Volume
If you have a mirrored logical volume and want to add more mirrors (i.e., create RAID 1+N), you can use lvconvert with the --addmirror option.
Example: Add a Mirror to an Existing LV
sudo lvconvert --addmirror 1 /dev/vgname/lvname--addmirror 1: Adds one additional mirror to the logical volume.You can add multiple mirrors (e.g.,
--addmirror 2for two additional mirrors).
6. Remove a Mirror from a Logical Volume
If you want to reduce the number of mirrors in a mirrored LV, you can use the --removemirror option.
Example: Remove a Mirror
sudo lvconvert --removemirror /dev/vgname/lvname--removemirror: Removes one mirror copy of the logical volume. You cannot remove the last mirror if there's only one mirror left.
7. Convert to a Striped Logical Volume (RAID 0)
You can also convert a logical volume to a striped volume (RAID 0) for better performance.
Example: Convert to Striped Volume
sudo lvconvert --stripes 2 /dev/vgname/lvname--stripes 2: Specifies that the volume should be striped across two devices. You can increase this number for more stripes.
8. Convert to a Linear Volume (Remove Striping)
If you want to revert a striped logical volume to a regular linear volume, you can use the --type option:
Example: Convert to a Linear Volume
sudo lvconvert --type linear /dev/vgname/lvname--type linear: Converts a striped or mirrored volume back to a linear volume, removing any striping or mirroring configuration.
Example Outputs
Successfully converting to a mirrored volume:
Conversion of /dev/vgname/lvname to a mirrored volume successful.Successfully converting to a thin volume:
Logical volume /dev/vgname/lvname converted to thin provisioning.Adding a mirror to an existing volume:
Logical volume /dev/vgname/lvname now has 2 mirrors.
Conclusion
The lvconvert command is a powerful tool in LVM that allows you to modify the characteristics of an existing logical volume, including converting it to a mirrored, striped, or thin-provisioned volume. It can also be used to add or remove mirrors from an existing logical volume, providing flexibility for RAID configurations and space management.
Key use cases include:
Converting to or from mirrored (RAID 1) volumes.
Converting to or from thin-provisioned volumes.
Adding or removing mirrors and stripes for performance or redundancy purposes.
Last updated