Dell EqualLogic PS6210XS EqualLogic Group Manager Administrator s Guide PS Ser - Page 40

A NAS cluster can serve data to multiple clients simultaneously, with no performance degradation. Clients connect to NAS storage through the NAS protocols of their operating system: • UNIX users access NAS storage through the NFS protocol. • Windows users access NAS storage through the SMB protocol. After the client establishes the preliminary connection, the NAS storage acts as a normal storage subsystem, accessed in the usual way by users or applications. The NAS cluster hardware and network configuration is described in detail in your NAS appliance hardware documentation and includes the following components: • NAS controller pair • Client network Used for client access to the NFS exports and SMB shares hosted by the NAS cluster. For security, the client network is typically separate from the SAN and internal network. • SAN/internal network Enables internal communication between the controllers as required for failover, communication between controllers, and communication between the NAS cluster and the PS Series SAN. The SAN/internal network is connected to the same set of switches. For performance and security reasons, Dell strongly recommends that this network be in a different subnet from the client network. A NAS cluster supports various network topologies. From a performance perspective, it is important to consider the subnets to which the clients belong (they might belong to more than one) and the subnets to which the NAS cluster belongs. For example, if the NAS cluster and all clients are on the same subnet, the network is considered "flat," which provides the best performance. If clients reside on a subnet that is not the same as the NAS cluster client subnet, the network is routed, and clients can access NAS container data by using a router or layer 3 switches. In a routed network configuration, you should configure multiple NAS cluster IP addresses for proper load balancing. Network interfaces in a NAS controller are numbered. Each interface has a specific function and is used for a client network, SAN network, internal network, or IPMI connection. If you understand the function of each network interface, you can ensure a highly available network configuration in which no single switch failure or network cable disconnection results in a service disruption. About NAS Controllers A NAS controller has preinstalled NAS firmware and redundant, battery-backed, hot-swappable hardware. NAS controllers do not require day-to-day maintenance. The group logs alarms and events related to the NAS controllers. When a NAS appliance is functioning properly, both NAS controllers serve NAS container data. Data caching across controllers provides high performance, and cache mirroring between controllers ensures data redundancy. Each NAS appliance contains two controllers that handle client connections, manage read and write disk operations, and interact with servers and workstations. I/O load-balancing mechanisms direct client requests to the least busy NAS controller, which maintains an even load balance across all NAS controllers in the NAS cluster. If one controller in a NAS appliance fails, clients fail over automatically to the peer NAS controller, and cache mirroring stops (journaling mode). When failover occurs, some SMB clients automatically reconnect to the peer NAS controller. In other cases, an SMB application might fail, and you must restart it. NFS clients experience a temporary pause during failover, but client network traffic resumes automatically. NOTE: Not all NAS cluster management operations are supported while a NAS controller is down or detached. Therefore, it is important to replace a failed NAS controller as soon as possible. You can perform the following NAS controller operations: 40 Architecture Fundamentals