When people look at racks of cluster nodes, they often ask "How do you tell which node is which?" A very good question. It turns out that there are internal and external ways to identify cluster nodes. The external method is for physically locating the node in a rack. If a node is having problems the system administrator may need to attach a monitor or look at case lights. Without help, identifying a node can somewhat difficult. In the early days, system administrators often had to know the physical location of the node in a rack, then go to the rack and count nodes until the node was identified. In some cases, the node was labeled with a sequential ID number so it could be easily located.

New servers often have a "trouble" or identification light that is highly visible. The identify light is controlled by IPMI, an out-of-band (OOB) node access method that talks with a baseboard management controller (BMC). The BMC is independent of the system CPUs and powered as soon as the node is plugged in to main power. The system administrator can turn the light on from the BMC management console or depress a switch directly on the node.

When a problem is detected on a node, the system administrator is usually notified in some fashion. Either through the BMC software or some other node monitoring software. The administrator may then turn on the identification light to locate the server in the rack and obvious things like cables can then be checked. Other methods of identification are also available and were used in the past when IPMI was not available. Powering down the node was one option so it could be identified by its "no lights."

Internally, clusters are identified using software. All nodes have a unique network name and address often assigned when the node is provisioned. The network address or IP address is unique for each node. The network name can either be a fully qualified domain name (FQDN) and/or a "nickname". For instance, a node can appear in the /etc/hosts file as follows, (IP address, FQDN, nickname):

10.1.0.72    node08.somedomain.com   node08

Once the node is booted it is identified by its IP address (network address) and hostname (nickname). Hostnames are often of the form "node001" or similar so that they can be easily identified. Some hostnames are designed to identify the node and rack location as "n24r12" which means "node 24 in rack 12".

As clusters get larger, identifying nodes, both externally and internally becomes important. Translating from an internal IP address to a physical location in a rack is an important and sometimes overlooked "feature" for the first time cluster administrator. Just as important, is being able to convert from the rack location to the node IP address. Often times a simple label with both IP address and the nodes unique Ethernet address (often called MAC address)  is the best solution. Through good planing an understanding of the physical and network layout, locating troubled nodes can be one of the easier parts of your job.

The Intel® Cluster Ready Program enables faster, easier deployment of higher performance HPC clusters based on the Intel® Xeon® processor 5500 series. Intel Cluster Ready makes it simpler to choose, deploy and manage HPC clusters, and ensures application and system interoperability. In doing so, it enables companies to rapidly capitalize on the Intel Xeon processor 5500 series and use it to solve bigger problems, expedite total application performance, and reduce TCO. Bottom line: simpler, more powerful and more cost-effective high performance computing. The Intel Cluster Ready certification gives customers another reason to deploy the Appro GreenBlade solution by offering confidence that the cluster architecture and software are certified to work together. It also gives Independent Software Vendors (ISV) the ability to run their software in this certified cluster platform providing a fast and cost-effective implementation for industry-specific solutions.
Not all blades are created equal. In the HPC sector, blades need to be both green and provide high performance. The Appro GreenBlade System provides an extremely flexible and manageable way to create high-density computing. It is designed to scale, with little effort or re-configuration.
The Appro cluster solution based on the GreenBlade building block offers a variety of interconnect options to include only standard 1U Ethernet or 1U Infiniband (IB) switches. This is accomplished by pre-allocating space in each rack cabinet for two standard 24-port Infiniband or Ethernet switches. This offers flexibility for customers who may choose to deploy either an Ethernet or IB-based HPC cluster. Appro also offers variations in the Infiniband interconnect with ConnectX DDR single IB, DDR dual IB or QDR single IB configurations. The Appro GreenBlade is unique in this category; each blade can provide one or two QDR InfiniBand ports on the motherboard and thus do not require any additional PCIe HCAs to be added to the blade. All these options provide excellent network bandwidth and low latency at an affordable price point to many HPC workloads that require higher performance for their applications.
In addition, the Appro GreenBlade offers standards-based Intelligent Platform Management Interface (IPMI) with a choice of Appro’s remote server management or open source cluster management software solutions.
Long considered to be primarily useful only for HPC-scale deployments, blades are beginning to make inroads into the midsize HPC segment. With the introduction of blade products designed specifically for the needs of this market, such as the Appro GreenBlade system, midsize HPC customers are more likely to turn to blades for their day-to-day server infrastructure needs. The Appro GreenBlade is suited for small to midsize departmental and workgroup high performance computing data centers looking for flexibility of system configuration and network connectivity. This addresses the need for performance, reliability, floor space, power and cooling limitations, storage and remote management options at an affordable price. In addition, the Appro GreenBlade is ideal for HPC applications that require high bandwidth and low latency access to system memory, clustering, and Storage Area Networks (SAN).