Storage Virtual Machines (SVMs, formerly known as Vservers) contain data volumes and one or more LIFs through which they serve data to the clients. Starting with clustered Data ONTAP 8.1.1, SVMs can either contain one or more FlexVol volumes, or a single Infinite Volume.
SVMs securely isolate the shared virtualized data storage and network, and each SVM appears as a single dedicated server to the clients. Each SVM has a separate administrator authentication domain and can be managed independently by its SVM administrator.
In a cluster, SVMs facilitate data access. A cluster must have at least one SVM to serve data. SVMs use the storage and network resources of the cluster. However, the volumes and LIFs are exclusive to the SVM. Multiple SVMs can coexist in a single cluster without being bound to any node in a cluster. However, they are bound to the physical cluster on which they exist.
A cluster can have one or more SVMs with FlexVol volumes and SVMs with Infinite Volume.
Each SVM with FlexVol volumes in a NAS environment presents a single directory hierarchical view and has a unique namespace. The namespace enables NAS clients to access data without specifying the physical location of the data. The namespace also enables the cluster and SVM administrators to manage distributed data storage as a single directory with multiple levels of hierarchy.
The volumes within each NAS SVM are related to each other through junctions and are mounted on junction paths. These junctions present the file system in each volume. The root volume of the SVM is a FlexVol volume that resides at the top level of the namespace hierarchy; additional volumes are mounted to the SVM root volume to extend the namespace. As volumes are created for the SVM, the root volume of the SVM contains junction paths.
SVMs with FlexVol volumes can contain files and LUNs. They provide file-level data access by using NFS and CIFS protocols for the NAS clients, and block-level data access by using iSCSI and Fibre Channel (FC) (FCoE included) for SAN hosts.
SVMs with Infinite Volume can contain only one Infinite Volume to serve data. Each SVM with Infinite Volume includes only one junction path, which has a default value of /NS. The junction provides a single mount point for the large namespace provided by the SVM with Infinite Volume. You cannot add more junctions to an SVM with Infinite Volume. However, you can increase the size of the Infinite Volume.
SVMs with Infinite Volume can contain only files. They provide file-level data access by using NFS and CIFS protocols. SVMs with Infinite Volume cannot contain LUNs and do not provide block-level data access.