12 Managing Storage #

To add a storage pool, proceed as follows:

Virtual Machine Manager's Storage Manager lets you create or delete volumes in a pool. You may also temporarily deactivate or permanently delete existing storage pools. Changing the basic configuration of a pool is currently not supported by SUSE.

12.1.2.1 Starting, Stopping and Deleting Pools #

 

The purpose of storage pools is to provide block devices located on the VM Host Server that can be added to a VM Guest when managing it from remote. To make a pool temporarily inaccessible from remote, click Stop in the bottom left corner of the Storage Manager. Stopped pools are marked with State: Inactive and are grayed out in the list pane. By default, a newly created pool will be automatically started On Boot of the VM Host Server.

To start an inactive pool and make it available from remote again, click Start in the bottom left corner of the Storage Manager.

Note: A Pool's State Does not Affect Attached Volumes

Volumes from a pool attached to VM Guests are always available, regardless of the pool's state (Active (stopped) or Inactive (started)). The state of the pool solely affects the ability to attach volumes to a VM Guest via remote management.

To permanently make a pool inaccessible, click Delete in the bottom left corner of the Storage Manager. You may only delete inactive pools. Deleting a pool does not physically erase its contents on VM Host Server—it only deletes the pool configuration. However, you need to be extra careful when deleting pools, especially when deleting LVM volume group-based tools:

Warning: Deleting Storage Pools

Deleting storage pools based on local file system directories, local partitions or disks has no effect on the availability of volumes from these pools currently attached to VM Guests.

Volumes located in pools of type iSCSI, SCSI, LVM group or Network Exported Directory will become inaccessible from the VM Guest if the pool is deleted. Although the volumes themselves will not be deleted, the VM Host Server will no longer have access to the resources.

Volumes on iSCSI/SCSI targets or Network Exported Directory will become accessible again when creating an adequate new pool or when mounting/accessing these resources directly from the host system.

When deleting an LVM group-based storage pool, the LVM group definition will be erased and the LVM group will no longer exist on the host system. The configuration is not recoverable and all volumes from this pool are lost.

12.1.2.3 Deleting Volumes From a Storage Pool #

 

Deleting a volume can only be done from the Storage Manager, by selecting a volume and clicking Delete Volume. Confirm with Yes.

Warning: Volumes Can Be Deleted Even While in Use

Volumes can be deleted even if they are currently used in an active or inactive VM Guest. There is no way to recover a deleted volume.

Whether a volume is used by a VM Guest is indicated in the Used By column in the Storage Manager.

List all pools currently active by executing the following command. To also list inactive pools, add the option --all:

virsh pool-list --details

Details about a specific pool can be obtained with the pool-info subcommand:

virsh pool-info POOL

Volumes can only be listed per pool by default. To list all volumes from a pool, enter the following command.

virsh vol-list --details POOL

At the moment virsh offers no tools to show whether a volume is used by a guest or not. The following procedure describes a way to list volumes from all pools that are currently used by a VM Guest.

Use the virsh pool subcommands to start, stop or delete a pool. Replace POOL with the pool's name or its UUID in the following examples:

virsh offers two ways to add volumes to storage pools: either from an XML definition with vol-create and vol-create-from or via command line arguments with vol-create-as. The first two methods are currently not supported by SUSE, therefore this section focuses on the subcommand vol-create-as.

To add a volume to an existing pool, enter the following command:

virsh vol-create-as POOL1NAME2 12G --format3raw|qcow2|qed4 --allocation 4G5

virsh vol-clone NAME_EXISTING_VOLUME1NAME_NEW_VOLUME2 --pool POOL3

To permanently delete a volume from a pool, use the subcommand vol-delete:

virsh vol-delete NAME --pool POOL

--pool is optional. libvirt tries to locate the volume automatically. If that fails, specify this parameter.

Warning: No Checks Upon Volume Deletion

A volume will be deleted in any case, regardless of whether it is currently used in an active or inactive VM Guest. There is no way to recover a deleted volume.

Whether a volume is used by a VM Guest can only be detected by using by the method described in Procedure 12.1, “Listing all Storage Volumes Currently Used on a VM Host Server”.

After you create a volume as described in Section 12.2.3, “Adding Volumes to a Storage Pool”, you can attach it to a virtual machine and use it as a hard disk:

virsh attach-disk DOMAIN SOURCE_IMAGE_FILE TARGET_DISK_DEVICE

For example:

virsh attach-disk sles12sp3 /virt/images/example_disk.qcow2 sda2

To check if the new disk is attached, inspect the result of the virsh dumpxml command:

root # virsh dumpxml sles12sp3
[...]
<disk type='file' device='disk'>
 <driver name='qemu' type='raw'/>
 <source file='/virt/images/example_disk.qcow2'/>
 <backingStore/>
 <target dev='sda2' bus='scsi'/>
 <alias name='scsi0-0-0'/>
 <address type='drive' controller='0' bus='0' target='0' unit='0'/>
</disk>
[...]

12.2.5.1 Hotplug or Persistent Change #

 

You can attach disks to both active and inactive domains. The attachment is controlled by the --live and --config options:

--live

Hotplugs the disk to an active domain. The attachment is not saved in the domain configuration. Using --live on an inactive domain is an error.

--config

Changes the domain configuration persistently. The attached disk is then available after the next domain start.

--live--config

Hotplugs the disk and adds it to the persistent domain configuration.

Tip: virsh attach-device

virsh attach-device is the more generic form of virsh attach-disk. You can use it to attach other types of devices to a domain.

To detach a disk from a domain, use virsh detach-disk:

root # virsh detach-disk DOMAIN TARGET_DISK_DEVICE

For example:

root # virsh detach-disk sles12sp3 sda2

You can control the attachment with the --live and --config options as described in Section 12.2.5, “Attaching Volumes to a VM Guest”.

Locking virtual disks is not enabled by default on SUSE Linux Enterprise Server. To enable and automatically start it upon rebooting, perform the following steps:

By default virtlockd is configured to automatically lock all disks configured for your VM Guests. The default setting uses a "direct" lockspace, where the locks are acquired against the actual file paths associated with the VM Guest <disk> devices. For example, flock(2) will be called directly on /var/lib/libvirt/images/my-server/disk0.raw when the VM Guest contains the following <disk> device:

<disk type='file' device='disk'>
 <driver name='qemu' type='raw'/>
 <source file='/var/lib/libvirt/images/my-server/disk0.raw'/>
 <target dev='vda' bus='virtio'/>
</disk>

The virtlockd configuration can be changed by editing the file /etc/libvirt/qemu-lockd.conf. It also contains detailed comments with further information. Make sure to activate configuration changes by reloading virtlockd:

systemctl reload virtlockd

Note: Locking Currently Only Available for All Disks

Currently, locking can only be activated globally, so that all virtual disks are locked. Support for locking selected disks is planned for future releases.

file_lockspace_dir = "/MY_LOCKSPACE_DIRECTORY"

lvm_lockspace_dir = "/MY_LOCKSPACE_DIRECTORY"
iscsi_lockspace_dir = "/MY_LOCKSPACE_DIRECTORY"