How to use the command 'qm move_disk' (with examples)

The qm move_disk command, an alias of qm disk move, is a tool used in Proxmox VE (Virtual Environment) for relocating virtual machine disks. It allows administrators to move disk images between different storage backends, thus optimizing storage management. This command can be instrumental in managing resources efficiently, performing maintenance tasks, or optimizing system performance. In this article, we will explore a variety of use cases to illustrate its utility.

Use case 1: Move a Disk to a Different Storage

Code:

qm move_disk 100 scsi0 local-zfs

Motivation:

Suppose you are managing a Proxmox server where different types of storage are available such as local SSDs, traditional HDD, and network-attached storage (NAS). Moving disks from slower storage to faster storage can improve performance. Conversely, relocating disks can free up premium storage for high-performance tasks. The qm move_disk command facilitates these kinds of optimizations by allowing administrators to move virtual machine disks to different storage backends seamlessly.

Explanation:

• 100: The unique identifier of the virtual machine whose disk is being moved.
• scsi0: This indicates the specific disk attached to the virtual machine via the SCSI interface that needs relocation.
• local-zfs: Specifies the target storage pool, in this case, a local ZFS storage, to which the disk will be migrated.

Example Output:

Moving disk 100:scsi0 to local-zfs...
  Logical volume "vm-100-disk-0" successfully moved.
  Moved to local-zfs:vm-100-disk-0

Use case 2: Move a Disk with Byte Size Specification

Code:

qm move_disk 101 ide0:target_storage -bytes 1048576000

Motivation:

In scenarios where bandwidth or connectivity is a concern, specifying the exact byte size for a disk while moving could be crucial. This ensures that you are aware of how much data is being migrated and helps in planning network usage and time estimations, particularly when moving data over slower networks.

Explanation:

• 101: Denotes the virtual machine ID.
• ide0: References the IDE interface disk that needs shifting.
• target_storage: Specifies the intended storage destination.
• -bytes 1048576000: An optional argument used here to specify the total byte size of the disk being moved.

Example Output:

Checking disk size...
Calculated disk size is 1048576000 bytes.
Moving disk 101:ide0 to target_storage...
  Disk move completed successfully.

Use case 3: Move a Disk with Properties Changed

Code:

qm move_disk 102 sata0 new-storage --delete-source

Motivation:

This example is useful when not only moving a disk but also cleaning up the source. Operations that involve changing disk locations typically leave the original data intact. The --delete-source option ensures that the initial location is cleared post-move. This is beneficial for saving space and maintaining a tidy storage system, especially in high-density environments.

Explanation:

• 102: The VM ID whose disk is to be moved.
• sata0: Identifies the SATA disk interface that is targeted for migration.
• new-storage: Specifies the destination storage where the disk should be moved.
• --delete-source: A flag that ensures the original disk is deleted after the move completes, keeping the storage organized.

Example Output:

Starting disk migration...
Disk 102:sata0 successfully moved to new-storage.
Source disk deleted as per '--delete-source' flag.

Conclusion:

The qm move_disk command is a powerful tool for managing virtual machine storage within Proxmox VE environments. By allowing administrators to dynamically relocate disk storage, this command supports efficient resource management. Each use case demonstrates different motivations—ranging from enhancing performance and planning network operations to maintaining order in storage systems. Mastery of this command can significantly bolster the ability to efficiently manage a virtualized infrastructure setup.