Overview

How Should I Read This Chapter

Before performing the operations outlined in this chapter, familiarize with Node Deployment from the Installation guide.

After that, proceed with the specific Datastore documentation you might be interested in.

Datastore Types

Storage in OpenNebula is designed around the concept of datastores. A datastore is any storage medium to store disk images. OpenNebula distinguishes between three different datastore types:

  • Images Datastore, which stores the base operating system images, persistent data volumes, CD-ROMs and File Systems.
  • System Datastore holds disks of running Virtual Machines. Disk are moved from/to the Images when the VMs are deployed/terminated.
  • Files & Kernels Datastore to store plain files (not disk images), e.g. kernels, ramdisks, or contextualization files. See details here.
Overview of Storage Design based on Datastores

Storage portfolio

Use case Description Shared Disk Format Disk snapshots VM snapshots Storage migration Fault tolerance HV Availability
Local storage Images stored in Front-end* and transferred to hosts via
SSH on instantiation.		 no raw/qcow2 yes yes poweroff/live no KVM/LXC EE/CE
NFS/NAS Images stored in a NFS share, activated directly. yes raw/qcow2 yes yes poweroff/live yes KVM/LXC EE/CE
Ceph Images stored in a Ceph pool, activated directly. yes raw (RBD) yes no poweroff yes KVM/LXC EE/CE
SAN - LVM Images stored as LVs in a SAN, activated directly. yes raw (LV) yes no poweroff yes KVM EE only
SAN - LVM
(File Mode)		 Images stored in frontend*, transferred to hosts via SSH,
and copied to the SAN on instantiation.		 yes raw (LV)
Images: raw/qcow2		 yes** no poweroff/live yes KVM EE/CE
SAN - NetApp Images stored in a NetApp cabin, activated directly. yes raw (LUN) yes no poweroff/live yes KVM EE only
SAN - Everpure Images stored in a Pure FlashArray, activated directly. yes raw (LUN) yes no poweroff/live yes KVM EE only
FileSystems - VirtioFS Images are filesytem paths available on the hosts yes filesystems (dir) no no no yes KVM EE/CE

* Additional options available by mounting remote filesystems in the Front-end.

** Only with LVM Thin mode enabled.

*** Images stored on the frontend just contain metadata. The filesystems to mount should be present and available on the hosts.

For details on performing datastore migrations, refer to the datastore migration section of the Virtual Machines Operation Documentation.

Other storage options

As an admin, restrict the usage of some storage options because these give low-level access to hosts and could become a serious security risk. Please read carefully the corresponding documentation before using them:

Use case Description Shared Disk Format Disk snapshots VM snapshots Live migration Fault tolerance HV Availability
Raw Device Mapping Images accessed as block devices directly from hosts. yes raw (block) yes no yes no KVM EE/CE
SAN - iSCSI Images accessed as iSCSI LUNs directly from hosts. yes raw (volume) yes no yes yes KVM EE/CE