libvirt Storage Pools: dir, LVM, NFS, ZFS, RBD

libvirt manages VM disks through storage pools (where disks live) and volumes (the disks themselves). Understanding libvirt storage pools lets you mix local files, LVM, NFS and distributed storage with the same tools.

Before you start

A KVM host with libvirt; see install KVM on Ubuntu.
Background on formats: qcow2 vs raw.

Pool types

Type	Backed by	Volumes are	Notes
dir	A local directory	qcow2/raw files	Default pool at /var/lib/libvirt/images
logical	LVM volume group	Logical volumes	Fast block storage; see LVM pool
netfs	NFS (or other network FS)	Files	Shared storage for migration; see NFS storage
iscsi / iscsi-direct	iSCSI target	LUNs	See iSCSI
zfs	A ZFS pool	zvols	Snapshots, compression; see ZFS for VMs
rbd	Ceph cluster	RBD images	Distributed; see Ceph
disk / fs	Whole disk or a device with a filesystem	Partitions / files	Less common

Common commands

virsh pool-list --all --details

virsh pool-info default

virsh vol-list default --details

Create a volume and delete one:

virsh vol-create-as default app01.qcow2 30G --format qcow2

virsh vol-delete app01.qcow2 --pool default

Define a new directory pool

virsh pool-define-as fastpool dir --target /srv/vm-fast

virsh pool-build fastpool && virsh pool-start fastpool && virsh pool-autostart fastpool

Define a ZFS pool

virsh pool-define-as zpool zfs --source-name vmpool

This assumes an existing ZFS pool named vmpool; libvirt will create zvols in it. ZFS support requires libvirt built with the ZFS backend.

Refresh after external changes

If you create files or LVs outside libvirt, refresh so they appear:

virsh pool-refresh default

Choosing

Single host, simple: dir with qcow2 or logical with raw.
Snapshots and integrity: ZFS.
Live migration across hosts: netfs, iSCSI with shared LVM, or RBD.

Troubleshooting

Pool inactive after reboot: run virsh pool-autostart.
"storage pool does not support volume creation": some types (like iscsi) only expose existing LUNs.
Permission errors: check ownership and SELinux/AppArmor labels on the target path.

Frequently asked questions

Do I need pools at all?

No, VMs can reference disk paths directly, but pools make management and tooling easier.

Can one VM use disks from several pools?

Yes, each disk can come from a different pool.

How do VPS panels handle storage?

They usually manage LVM, ZFS or files themselves; see VirtFusion storage.

Next steps

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