Storage virtualization overview
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You use storage virtual machines (SVMs) to serve data to clients and hosts. Like a virtual machine running on a hypervisor, an SVM is a logical entity that abstracts physical resources. Data accessed through the SVM is not bound to a location in storage. Network access to the SVM is not bound to a physical port.
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SVMs were formerly called "vservers." The ONTAP command line interface still uses the term "vserver". |
An SVM serves data to clients and hosts from one or more volumes, through one or more network logical interfaces (LIFs). Volumes can be assigned to any data aggregate in the cluster. LIFs can be hosted by any physical or logical port. Both volumes and LIFs can be moved without disrupting data service, whether you are performing hardware upgrades, adding nodes, balancing performance, or optimizing capacity across aggregates.
The same SVM can have a LIF for NAS traffic and a LIF for SAN traffic. Clients and hosts need only the address of the LIF (IP address for NFS, SMB, or iSCSI; WWPN for FC) to access the SVM. LIFs keep their addresses as they move. Ports can host multiple LIFs. Each SVM has its own security, administration, and namespace.
In addition to data SVMs, ONTAP deploys special SVMs for administration:
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An admin SVM is created when the cluster is set up.
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A node SVM is created when a node joins a new or existing cluster.
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A system SVM is automatically created for cluster-level communications in an IPspace.
You cannot use these SVMs to serve data. There are also special LIFs for traffic within and between clusters, and for cluster and node management.
Why ONTAP is like middleware
The logical objects ONTAP uses for storage management tasks serve the familiar goals of a well-designed middleware package: shielding the administrator from low-level implementation details and insulating the configuration from changes in physical characteristics like nodes and ports. The basic idea is that the administrator should be able to move volumes and LIFs easily, reconfiguring a few fields rather than the entire storage infrastructure.