Managing VMFS Volumes

Different commands are available for listing, mounting, and unmounting VMFS volumes and for listing, mounting, and unmounting VMFS snapshot volumes.

■	Managing VMFS volumes

esxcli storage filesystem list shows all volumes, mounted and unmounted, that are resolved, that is, that are not snapshot volumes.

esxcli storage filesystem unmount unmounts a currently mounted filesystem. Use this command for snapshot volumes or resolved volumes.

■	Managing snapshot volumes

esxcli storage vmfs snapshot commands can be used for listing, mounting, and resignaturing snapshot volumes. See Mounting Datastores with Existing Signatures and Resignaturing VMFS Copies.

Managing Duplicate VMFS Datastores

Each VMFS datastore created in a LUN has a unique UUID that is stored in the file system superblock. When the LUN is replicated or when a snapshot is made, the resulting LUN copy is identical, byte-for-byte, to the original LUN. As a result, if the original LUN contains a VMFS datastore with UUID X, the LUN copy appears to contain an identical VMFS datastore, or a VMFS datastore copy, with the same UUID X.

ESXi hosts can determine whether a LUN contains the VMFS datastore copy, and either mount the datastore copy with its original UUID or change the UUID to resignature the datastore.

When a LUN contains a VMFS datastore copy, you can mount the datastore with the existing signature or assign a new signature. The vSphere Storage documentation discusses volume resignaturing in detail.

Mounting Datastores with Existing Signatures

You can mount a VMFS datastore copy without changing its signature if the original is not mounted. For example, you can maintain synchronized copies of virtual machines at a secondary site as part of a disaster recovery plan. In the event of a disaster at the primary site, you can mount the datastore copy and power on the virtual machines at the secondary site.

Important You can mount a VMFS datastore only if it does not conflict with an already mounted VMFS datastore that has the same UUID.

When you mount the VMFS datastore, ESXi allows both read and write operations to the datastore that resides on the LUN copy. The LUN copy must be writable. The datastore mounts are persistent and valid across system reboots.

You can mount a datastore with vicfg-volume (see To mount a datastore with vicfg-volume) or with ESXCLI (see To mount a datastore with ESXCLI).

Mounting and Unmounting with ESXCLI

The esxcli storage filesystem commands support mounting and unmounting volumes. You can also specify whether to persist the mounted volumes across reboots by using the --no-persist option.

Use the esxcli storage filesystem command to list mounted volumes, mount new volumes, and unmount a volume. Specify one of the connection options listed in Connection Options for vCLI Host Management Commands in place of <conn_options>.

To mount a datastore with ESXCLI

1	List all volumes that have been detected as snapshots.

esxcli <conn_options> storage filesystem list

2	Run esxcli storage filesystem mount with the volume label or volume UUID.

By default, the volume is mounted persistently; use --no-persist to mount nonpersistently.

esxcli <conn_options> storage filesystem volume mount --volume-label=<label>|--volume-uuid=<VMFS-UUID>

This command fails if the original copy is online.

You can later run esxcli storage filesystem volume unmount to unmount the snapshot volume.

esxcli <conn_options> storage filesystem volume unmount --volume-label=<label>|--volume-uuid=<VMFS-UUID>

Mounting and Unmounting with vicfg-volume

Use the vicfg-volume command to list mounted volumes, mount new volumes, and unmount a volume. Specify one of the connection options listed in Connection Options for vCLI Host Management Commands in place of <conn_options>.

To mount a datastore with vicfg-volume

1	List all volumes that have been detected as snapshots or replicas.

vicfg-volume <conn_options> --list

2	Run vicfg-volume --persistent-mount with the VMFS-UUID or label as an argument to mount a volume.

vicfg-volume <conn_options>  --persistent-mount <VMFS-UUID|label>

This command fails if the original copy is online.

You can later run vicfg-volume --unmount to unmount the snapshot or replica volume.

vicfg-volume <conn_options> --unmount <VMFS-UUID|label>

The vicfg-volume command supports resignaturing a snapshot volume and mounting and unmounting the volume. You can also make the mounted volume persistent across reboots and query a list of snapshot volumes and original volumes.

Resignaturing VMFS Copies

Use datastore resignaturing to retain the data stored on the VMFS datastore copy. When resignaturing a VMFS copy, the ESXi host assigns a new UUID and a new label to the copy, and mounts the copy as a datastore distinct from the original. Because ESXi prevents you from resignaturing the mounted datastore, unmount the datastore before resignaturing.

The default format of the new label assigned to the datastore is snap-<snapID>-<oldLabel>, where <snapID> is an integer and <oldLabel> is the label of the original datastore.

When you perform datastore resignaturing, consider the following points:

■	Datastore resignaturing is irreversible.

■	The LUN copy that contains the VMFS datastore that you resignature is no longer treated as a LUN copy.

■	A spanned datastore can be resignatured only if all its extents are online.

■	The resignaturing process is crash and fault tolerant. If the process is interrupted, you can resume it later.

■	You can mount the new VMFS datastore without a risk of its UUID conflicting with UUIDs of any other datastore, such as an ancestor or child in a hierarchy of LUN snapshots.

You can resignature a VMFS copy with ESXCLI (see Resignaturing a VMFS Copy with ESXCLI) or with vicfg-volume see Resignaturing a VMFS Copy with vicfg-volume.

Resignaturing a VMFS Copy with ESXCLI

The esxcli storage vmfs snapshot commands support resignaturing a snapshot volume. Specify one of the connection options listed in Connection Options for vCLI Host Management Commands in place of <conn_options>.

To resignature a VMFS copy with ESXCLI

1	List unresolved snapshots or replica volumes.

esxcli <conn_options> storage vmfs snapshot list

2	(Optional) Unmount the copy.

esxcli <conn_options> storage filesystem unmount

3	Run the resignature command.

esxcli <conn_options> storage vmfs snapshot resignature --volume-label=<label>|--volume-uuid=<id>

The command returns to the prompt or signals an error.

After resignaturing, you might have to do the following:

■	If the resignatured datastore contains virtual machines, update references to the original VMFS datastore in the virtual machine files, including .vmx, .vmdk, .vmsd, and .vmsn.

■	To power on virtual machines, register them with the vCenter Server system.

Resignaturing a VMFS Copy with vicfg-volume

You can use vicfg-volume to mount, unmount, and resignature VMFS volumes.

To resignature a VMFS copy with vicfg-volume

1	Make sure the copy is not mounted.

2	Run vicfg-volume with the resignature option.

vicfg-volume <conn_options> --resignature <VMFS-UUID|label>

The command returns to the prompt or signals an error.