A direct-attached configuration dedicates entire port bandwidth to be used for a specific
connection. Planning must account for the volume of expected traffic before you decide how many
ports are used in a direct-attached configuration. Direct attached connections are supported on the
same speed at both ends.
The system offers multiple options in deciding how to create a direct-attached configuration.
Bandwidth requirements for a direct-attached configuration make it important to determine the volume
of expected traffic in deciding the number of ports. Ensure you have accounted for sufficient
bandwidth, in particular node to node as the bandwidth between nodes determines write speed for
replicated workloads.
For example, if a system to system direct-attached link is configured between nodes in an I/O
group, then the link carries cache replication traffic and it might carry inter-node traffic such as
FlashCopy data. Hence, enough system to system bandwidth needs to be available so that:
- Cache replication for host writes can occur without any bandwidth bottleneck
- All possible intra-node traffic can be carried without any bandwidth bottleneck.
The following guidelines are provided for direct-attached configurations.
Note: One or more Fibre
Channel host adapters must be installed for the system to support these direct attachment
configurations.
- Fibre Channel direct attachment to host systems.
The system allows direct attachment
connectivity between its Fibre Channel ports and host ports. Host systems can be connected to
16 Gbps to 64 Gbps Fibre
Channel
ports
on the system. No special configuration is needed for host systems that are using this
configuration.
- Fibre Channel direct attachment between nodes in a system.
Direct connection of the system
Fibre Channel ports without using a Fibre Channel switch is supported. Such direct connections
between the system nodes might be useful in small configurations where no Fibre Channel switch
exists. It can also be used to connect nodes in the same I/O group to provide a dedicated connection
for mirroring the fast write cache data. Ensure that sufficient bandwidth is provisioned between
nodes to accommodate all the intra-node traffic.
FlashSystem supports 16 Gb Fibre Channel ports.
For more information on supported configuration,
see IBM System Storage Interoperation Center (SSIC).
Note: Direct attached connections are supported on the same speed at both
ends.