Preventive Service Planning
Abstract
This document outlines the requirements when configuring direct attachment of Storwize and SAN Volume Controller Systems
Content
Table of contents
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Section
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Description |
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1
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Direct Attachment Definition |
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2
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Storwize and SAN Volume Controller Clustered Systems A/ Single IO Group Storwize System B/ Single IO group SVC system C/ Two IO group Storwize system |
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3
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Fibre Channel Direct Attachment of Storage Systems |
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4
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Fibre Channel Direct attachment for Replication |
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5
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Fibre Channel Direct Attachment for Hosts |
1. Direct Attachment Definition
Direct attachment is defined as fibre channel connection which does not require a fibre channel SAN.
Where a fibre channel port on the fibre channel adapter in the node or canister is directly attached via a single fibre channel cable to a fibre channel port on another fibre channel adapter.
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.
The following requirements are provided for direct-attached configurations.
2. Storwize and SAN Volume Controller Clustered systems:
Storwize and SVC systems will normally communicate between nodes using either- Internal PCIe connection on the midplane (Storwize only)
- Fibre Channel SAN
- Fibre Channel over Ethernet (FCoE) network. (Please see below for more rules about using FCoE for inter-node communication)
- Direct Attach Fibre Channel (if you meet the minimum software levels listed above)
IMPORTANT: Directly attaching an 8Gbps SVC or Storwize port directly to a 16Gbps SVC or Storwize port is not supported. Mixed speed inter-node connections must go through a Fibre Channel SAN.
Because of the bandwidth requirements when you are using direct-attached inter-node configurations, it is important to determine the volume of expected traffic in deciding the number of required ports. There must be enough bandwidth available so that it can carry all possible inter-node traffic without any bottleneck.
There are three different configurations which may use direct attach cables for inter-node communication, and these are detailed below
A/ Single IO group Storwize system
Cables can be directly attached between node canisters in the same control enclosure of a single IO group system as a backup in case the communication across the midplane is affected. Note that these connections will not be used when the midplane connections are functioning.
B/ Single IO group SVC system
Cables can be directly attached between nodes in a single IO group system. A SAN Volume Controller or Storwize System single I/O Group direct attach Fibre Channel configuration requires a minimum of two connections between nodes or canisters. Below is a diagram showing the required number of cables. The cables can be attached to any port on the node canister
Here a SAN Volume controller single I/O Group using direct connections
A direct attach single IO Group SVC configuration can be arranged such that no internode traffic will flow across the SAN. However Fibre Channel connections via the SAN will still be required for host and storage connectivity.
C/ Two IO group Storwize system
Storwize systems with two I/O groups may also use Direct attach Fibre Channel. This requires two connections from each node canister to each other node canister, making a total of 8 FC cables to use this configuration. Below is a diagram showing where the cables must be connected. The cables can be attached to any port on the node canister
Additional rules when using FCoE for inter-node communication
Where only Fibre Channel over Ethernet ( FCoE ) is used for creating a clustered system support is available only for a specific set of FCoE capable switches. Please refer to the notes section of the supported switch types in SSIC for detail of supported switch models for FCoE Clustering. Direct attachment using FCoE is not supported.
FCoE capable switches that are not listed as supported for FCoE Clustering, the switches can be used to optionally create a separate zone to provide additional redundancy for intra-cluster communications, however, Fibre Channel SAN connectivity is still required. FCoE Clustering for node to node communication is not supported for stretch cluster configurations.
3. Fibre channel direct attachment to Storage Subsystems
Any supported controller can be temporarily direct attached for the purposes of migrating the data from that controller onto the Storwize system.
The following controllers can be permanently directly attached:
- FlashSystem 900
4. Direct attachment for Replication
Partnerships between systems for Metro Mirror or Global Mirror replication can be used with any of the following technologies:
- Fibre Channel SAN
- IP replication
- FCoE (Note that FCoE links have a maximum distance of 300 meters unless the traffic is bridged onto FCIP or Fibre Channel)
- Direct Attach Fibre Channel
If you wish to use directly attached Fibre Channel cable between two SVC or Storwize systems, then you must observe the following restrictions:
- There must be at least two fibre channel cables between the two clusters. IBM recommends that there are at least as many inter-system cables as there are nodes in the smallest system.
- At least two nodes in cluster A must be connected to at least two nodes in cluster B
- An 8Gb/s port can not be directly connected to a 16Gb/s port
- Using directly attached FC cables for replication can significantly increase the amount of traffic between nodes in the same system.
IMPORTANT: Directly attaching an 8Gbps SVC or Storwize port directly to a 16Gbps SVC or Storwize port is not supported. Mixed speed inter-node connections must go through a Fibre Channel SAN.
Here is an example replication configuration with connections between a four node and six node cluster.
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SVC and Storwize systems allow direct attachment connectivity between its Fibre Channel ports and host ports. Host systems can be connected to 8 Gb or 16 Gb Fibre Channel ports on Storwize V7000.
For Direct Attach HBA and OS combinations please visit the System Storage Interoperation Centre.
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Document Information
Modified date:
28 March 2023
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