Netif Section

The Netif section identifies the network interfaces supported by the Sun HPC cluster and specifies the rank and striping attributes for each interface. The hpc.conf template that is supplied with Sun HPC ClusterTools 3.0 software contains a default list of supported network interfaces as well as their default ranking. Example 2-3 represents a portion of the default Netif section.

Example 2-3 Netif Section Example

Begin Netif
NAME           RANK     MTU       STRIPE     PROTOCOL     LATENCY WIDTHmidnn          0        16384     0          tcp          20          150
idn            10       16384     0          tcp          20          150
scin           20       32768     1          tcp          20          150
  :            :          :       :           :           :            :
scid           40       32768     1          tcp          20          150
  :            :          :       :           :           :            :
scirsm         45       32768     1          rsm          20          150
  :            :          :       :           :           :            :
  :            :          :       :           :           :            :
smc            220      4096      0          tcp          20          150
End Netif

Interface Names

The first column lists the names of possible network interface types.

Rank Attribute

The rank of an interface is the order in which that interface is to be preferred over other interfaces. That is, if an interface with a rank of 0 is available when a communication operation begins, it will be selected for the operation before interfaces with ranks of 1 or greater. Likewise, an available rank-1 interface will be used before interfaces with a rank of 2 or greater.

Because hpc.conf is a shared, cluster-wide configuration file, the rank specified for a given interface will apply to all nodes in the cluster.

Network ranking decisions are usually influenced by site-specific conditions and requirements. Although interfaces connected to the fastest network in a cluster are often given preferential ranking, raw network bandwidth is only one consideration. For example, an administrator might decide to dedicate one network that offers very low latency, but not the fastest bandwidth to all intra-cluster communication and use a higher-capacity network for connecting the cluster to other systems.

MTU Attribute

This is a placeholder column. Its contents are not used at this time.

Stripe Attribute

Sun HPC ClusterTools 3.0 software supports scalable communication between cluster nodes through striping of MPI messages over SCI interfaces, as described in the Sun HPC 3.0 SCI Guide. In striped communication, a message is split into smaller packets and transmitted in two or more parallel streams over a set of network interfaces that have been logically combined into a stripe-group.

The STRIPE column allows the administrator to include individual SCI network interfaces in a stripe-group pool. Members of this pool are available to be included in logical stripe groups. These stripe groups are formed on an as-needed basis, selecting interfaces from this stripe-group pool.

To include the SCI interface in a stripe-group pool, set its STRIPE value to 1. To exclude an interface from the pool, specify 0. Up to four SCI network interface cards per node can be configured for stripe-group membership.

When a message is submitted for transmission over the SCI network, an MPI protocol module distributes the message over as many SCI network interfaces as are available.

Stripe-group membership is made optional so you can reserve some SCI network bandwidth for non-striped use. To do so, simply set STRIPE = 0 on the SCI network interface(s) you wish to reserve in this way.

Protocol Attribute

This column identifies the communication protocol used by the interface. The scirsm interface employs the RSM (Remote Shared Memory) protocol. The others all use TCP (Transmission Control Protocol).

Latency Attribute

This is a placeholder column. Its contents are not used at this time.

Bandwidth Attribute

This is a placeholder column. Its contents are not used at this time.