Connecting To A Dx Storage Cluster; About The Primary Access Node (Pan); Requirements For Node Accessibility; Using The Dx Storage Software Development Kit (Sdk) - Dell DX6000 Application Manual

Chapter 2. Connecting to a DX Storage Cluster
The following topics in this chapter discuss how your application can connect to a DX Storage
cluster or node:
• Section 2.1, "About the Primary Access Node (PAN)"
• Section 2.2, "Requirements for Node Accessibility"

2.1. About the Primary Access Node (PAN)

Requests to store, retrieve, or delete objects in the cluster can initially be sent to any accessible
node. The cluster then decides which node is best suited to carry out the request, based on
resource availability and other factors. The node that initially fielded the request is referred to as the
primary access node (PAN). If the PAN did not field the request, it sends the application a redirect
request that includes the address of a node referred to as the secondary access node (SAN). In this
way, a DX Storage cluster performs automatic and intrinsic load balancing.
Any node in a DX Storage cluster can serve as a PAN. The PAN for a particular request is the first
node in the cluster that receives the request from the application. After a PAN receives a request, it
decides whether to service the request itself or to request the application to redirect it to one of the
other nodes in the cluster.
Because the PAN takes responsibility for having the application direct the request to another node
in the cluster, your application does not need to provide any load balancing solution. DX Storage
implements load balancing even when nodes are dynamically added or removed from the cluster.

2.2. Requirements for Node Accessibility

Because any node can be called on by the PAN to service any particular request, all nodes must
be accessible to the application client. The following sections discuss, in order of most preferred to
least preferred, the ways an application can locate a PAN to use for transactions:
• Section 2.2.1, "Using the DX Storage Software Development Kit (SDK)"
• Section 2.2.2, "Using Multicast-DNS (mDNS)"
• Section 2.2.3, "Using DNS Round Robin"
• Section 2.2.4, "Using a Pool of Static IP Addresses"
• Section 2.2.5, "Using a Single Static IP Address"

2.2.1. Using the DX Storage Software Development Kit (SDK)

You can integrate with DX Storage using the SDK because along with the convenience it provides,
your application can use the ProxyLocator or StaticLocator object to find a node with which
to communicate.
The SDK's new ProxyLocator subclass performs the following functions:
1. Performs a GET / to the SCSP Proxy to pre populate its local list of DX Storage node IP
addresses.
2. Dynamically maintains this list as redirects and other responses are received directly from DX
Storage nodes.
For more details, see the DX Object Storage SDK Overview.
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Version 5.0
December 2010