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SmartConnect is available in two versions:
Using SmartConnect successfully for load balancing across an entire cluster’s worth of storage nodes, or across a limited subset of interfaces on those nodes, requires the proper configuration of a number of interdependent components. This section describes those components.
While SmartConnect static pools use the same initial-connection balancing algorithms when queried for the zone name of the static SmartConnect pool, they do not provide path failover in the event of an interface failure on the cluster. Static pools assign a specific IP address to a specific node interface in a pool, and if that node interface goes offline, its SmartConnect static IP address goes offline as well.
Dynamic pools provide seamless failover only for NFSv3 clients. Other connection types, including SMB/NFSv4, do not support the failover mechanism that SmartConnect dynamic pools provide. Static pools are recommended for connecting those workloads.
SmartConnect leverages an organization’s existing DNS infrastructure by providing a layer of intelligence within the OneFS software application. The client attempts to connect to the PowerScale cluster using a SmartConnect name which appears to the client as the hostname of the cluster. It does so by requesting a lookup for that host name from the environment’s DNS server. The resident DNS server will forward the lookup request for the delegated zone to the delegated zone’s server of authority, in this case the SmartConnect Service IP (SSIP) address on the cluster. If the node providing the SmartConnect service becomes unavailable, the SSIP will move to a different node in the pool automatically.
SmartConnect pools can be configured on the cluster so that all pools are resolved via a single DNS delegation (if all DNS servers are connected to the same subnet), or via multiple DNS delegations (for configurations in which multiple DNS servers are used on multiple subnets connecting to the cluster). To mount a particular SmartConnect pool, regardless of connection protocol, simply use the FQDN corresponding to the name that was assigned the pool at the time of its creation.
Note: While the name of an existing SmartConnect pool can be changed at any time, this will break any persistent connections from client workstations the next time they are rebooted.
The SmartConnect service subnet is the name of the external network subnet whose SmartConnect service will answer DNS requests on behalf of the IP address pool. A pool can have only one SmartConnect service answering DNS requests, though this subnet can be changed at any time.
Note: If the service subnet option is not configured for given SmartConnect pool, then all incoming DNS requests to the cluster for that particular pool will be ignored.
In most circumstances, where the DNS infrastructure and PowerScale storage cluster all connect to one network, a single DNS delegation should be adequate for all SmartConnect pools. To ensure proper name resolution, configure all SmartConnect pools to use the same service subnet and ensure that the subnet’s service IP address is provided as the delegated name server address on the organization’s DNS servers.
The SmartConnect Service IP is the IP address that receives all incoming DNS requests from outside the cluster. SmartConnect answers these DNS requests for each IP address pool according to the pool's client connection policy.
The connection policy determines how incoming requests are distributed to across members of the address pool. The following options are available when setting the connection policy:
When choosing how the method by which IP addresses are assigned to member interfaces for the address it is important to understand the difference between “static IPs” and “dynamic IPs”.
Static IP address allocation will assign IP addresses when member interfaces are added to the IP pool. As members are added to the pool, this method allocates the next unused IP address from the pool to each new member. Once an IP address is allocated, the pool member keeps the address indefinitely unless:
Dynamic IP address allocation ensures that all IP addresses in the IP address pool are assigned to member interfaces, which allows clients to connect to any IP addresses in the pool and be guaranteed a response. If a node or an interface becomes unavailable, its IP addresses are automatically moved to other available member interfaces in the pool.
More information on SmartConnect pool for optimal availability and performance can be found in the Dell EMC PowerScale: Network Design Considerations white paper.