The particular way in which Oracle VM approaches storage is through plug-ins: Oracle has made storage configuration and integration as flexible and modular as possible by creating a Storage Connect plug-in for each different category and type of storage. These plug-ins are discussed in further detail in Section 4.3, “Storage Connect Plug-ins”.

Storage in Oracle VM refers to two different types of disk storage: the space available for environment resources such as templates and ISO files, and the logical or physical disks used by virtual machines.

For virtual machine disks Oracle VM offers you two choices:

The design decision of virtual versus physical storage access depends on your server virtualization use cases as well as the existing storage hardware at your disposal. Virtual storage enables quick and easy on-the-fly configuration but introduces a higher level of abstraction, since multiple filesystems are nested within each other. Therefore, when using virtual storage it is important to balance ease of use against the lower performance compared to physical storage. Physical storage access implies that virtual machine disk storage is mapped directly onto the LUNs configured in the physical storage hardware, which is exactly like the way physical servers access their storage. The advantage here is that existing procedures and storage management practices can be maintained.

Storage can be configured locally, specifically using an OCFS2 file system on a local disk of the Oracle VM Server. OCFS2 is used because the file system is accessed simultaneously by multiple VMs, something which most file systems cannot handle, but which OCFS2 is explicitly designed to handle. In general, it is far more reliable to use a separate location for a storage repository, so that it can be addressed by and attached to all Oracle VM Servers in the server pool. This is essential for live migration and HA configurations. Storage is configured with any of the following technologies:

To enable HA or live migration, you must make sure all Oracle VM Servers have access to the same storage resources. Specifically for live migration the Oracle VM Servers also must be part of the same server pool. Also note that clustered server pools require access to a shared file system where server pool information is stored and retrieved, for example in case of failure and subsequent server role changes. The server pool file system can either be on an NFS share or on a LUN of a SAN server. For more information about setting up file servers and SAN servers, see Section 4.6, “Managing Storage”.