Storage in Oracle VM can be provided using any of the following technologies:
Local disks.
Shared Network Attached Storage - NFS.
Shared iSCSI SANs: abstracted LUNs or raw disks accessible over existing network infrastructure.
Fibre Channel SANs connected to one or more host bus adapters (HBAs).
OCFS2 (Oracle Cluster File System) is used in the storage configurations that are not based on NFS.
While it is possible to use a local disk to create a repository for use by virtual machines on a particular Oracle VM Server, 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.
To configure access to different storage types across Oracle VM Servers within a deployment, Oracle VM makes use of Oracle Storage Connect plug-ins. Storage Connect plug-ins are packaged and distributed as RPM packages and deployed on the Oracle VM Servers. They are divided in two major categories: storage array plug-ins for any block based storage, and file system plug-ins for any network file system based storage.
The main benefits of the plug-in approach are:
Flexibility: Use and integrate with your existing storage infrastructure, choose between file-based and block-based solutions, and use local storage for testing purposes or virtual machines of minor importance. Use generic or vendor-specific plug-ins depending on your available hardware or any new hardware you select.
Scalability: Add more storage providers of your preferred type and present them to your server pools as your need for storage increases. Reduce the amount of storage again if the higher storage requirements are temporary. Provision your storage with redundancy and multipathing according to your requirements and preferences.
Extensibility: If you upgrade your storage, consider the added functionality of vendor-specific plug-ins. If you select hardware for which Oracle Storage Connect plug-ins are available, ask the manufacturer for the RPM and install the plug-in on the Oracle VM Servers with access to this storage hardware.
Oracle VM always requires a location to store environment resources that are essential to the creation and management of virtual machines. These resources include VM templates and assemblies, ISO files (virtual DVD images), VM configuration files and VM virtual disks. The location of such a group of resources is called a storage repository. You present a storage repository to the Oracle VM Servers that need access to those resources; typically all servers in a server pool.
Storage repositories can be configured on an NFS file system or on a physical disk (LUN) of a storage array. However, for storage repositories on physical disk, the servers with access to it must be members of a clustered server pool. For unclustered server pools only file server storage is available. For details about the use of storage repositories, see Section 3.9, “Where are Virtual Machine Resources Located?”.
Clustering adds another storage element to the environment: the server pool file system. During server pool creation, the server pool file system specified for the new server pool is accessed and formatted as an OCFS2 file system, whether the file system is accessed by the Oracle VM Servers as an NFS share, a FC LUN or iSCSI LUN. This formatting creates several management areas on the file system including a region for the global disk heartbeat. The server pool file system plays a key role in clustering and therefore in the high-availability configuration of the Oracle VM environment. For details about server pool clustering, see Section 6.8, “How do Server Pool Clusters Work?”.
The storage element that is most tangible and visible to all users of Oracle VM is the virtual machine disk. A VM disk is either a disk image file in a storage repository or a raw physical disk. If a physical disk (LUN) is used, it is attached directly to the VM in the same way it would be to a physical machine. For details about virtual machine operation, see Chapter 7, Understanding Virtual Machines. Again, the availability of VM disks in a storage location with shared access from all Oracle VM Servers in the server pool is essential for VM high-availability.
Storage is described in more detail in Chapter 3, Understanding Storage.