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pve-storage-dir.adoc

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Directory Backend

Storage pool type: dir

{pve} can use local directories or locally mounted shares for storage. A directory is a file level storage, so you can store any content type like virtual disk images, containers, templates, ISO images or backup files.

Note
 You can mount additional storages via standard linux '/etc/fstab', and then define a directory storage for that mount point. This way you can use any file system supported by Linux.

This backend assumes that the underlying directory is POSIX compatible, but nothing else. This implies that you cannot create snapshots at the storage level. But there exists a workaround for VM images using the qcow2 file format, because that format supports snapshots internally.

Tip
 Some storage types do not support O_DIRECT, so you can’t use cache mode none with such storages. Simply use cache mode writeback instead.

We use a predefined directory layout to store different content types into different sub-directories. This layout is used by all file level storage backends.

Table 1. Directory layout
Content type Subdir

VM images

images/<VMID>/

ISO images

template/iso/

Container templates

template/cache

Backup files

dump/

Configuration

This backend supports all common storage properties, and adds an additional property called path to specify the directory. This needs to be an absolute file system path.

Configuration Example ('/etc/pve/storage.cfg')
dir: backup
        path /mnt/backup
        content backup
        maxfiles 7

Above configuration defines a storage pool called backup. That pool can be used to store up to 7 backups (maxfiles 7) per VM. The real path for the backup files is '/mnt/backup/dump/…​'.

File naming conventions

This backend uses a well defined naming scheme for VM images:

vm-<VMID>-<NAME>.<FORMAT>
<VMID>

This specifies the owner VM.

<NAME>

This can be an arbitrary name (ascii) without white spaces. The backend uses disk-[N] as default, where [N] is replaced by an integer to make the name unique.

<FORMAT>

Species the image format (raw|qcow2|vmdk).

When you create a VM template, all VM images are renamed to indicate that they are now read-only, and can be uses as a base image for clones:

base-<VMID>-<NAME>.<FORMAT>
Note
 Such base images are used to generate cloned images. So it is important that those files are read-only, and never get modified. The backend changes the access mode to 0444, and sets the immutable flag (chattr +i) if the storage supports that.

Storage Features

As mentioned above, most file systems do not support snapshots out of the box. To workaround that problem, this backend is able to use qcow2 internal snapshot capabilities.

Same applies to clones. The backend uses the qcow2 base image feature to create clones.

Table 2. Storage features for backend dir
Content types Image formats Shared Snapshots Clones

images rootdir vztempl iso backup

raw qcow2 vmdk subvol

no

qcow2

qcow2

Examples

Please use the following command to allocate a 4GB image on storage local:

# pvesm alloc local 100 vm-100-disk10.raw 4G
Formatting '/var/lib/vz/images/100/vm-100-disk10.raw', fmt=raw size=4294967296
sucessfuly created 'local:100/vm-100-disk10.raw'
Note
 The image name must conform to above naming conventions.

The real file system path is shown with:

# pvesm path local:100/vm-100-disk10.raw
/var/lib/vz/images/100/vm-100-disk10.raw

And you can remove the image with:

# pvesm free local:100/vm-100-disk10.raw