SCSI Flow Services
An SCSI initiator and target combination is an SCSI flow. SCSI flow services provide enhanced features for SCSI flows, such as write acceleration and flow monitoring for statistics obtained on an SSM.
This section includes the following topics:
About SCSI Flow Services
The SCSI flow services functional architecture consists of the following components:
- SCSI flow manager (SFM) on the supervisor—The SFM resides on a supervisor module and handles the configuration of SCSI flows, validating them and relaying configuration information to the appropriate SSM. It also handles any dynamic changes to the status of the SCSI flow due to external events and registers changes that occur due to various operations.
- SCSI flow configuration CLI on the supervisor—The SFCC resides on the CPP of the SSM. It receives flow configuration requests from the SFM, programs the DPP corresponding to the initiator and target port interfaces, and responds to the SFM with the status of the configuration request.
- SCSI flow configuration client on the Control Path Processor (CPP) of an SSM.
- SCSI flow feature set support on the Data Path Processor (DPP) of an SSM—The DPP on the SSM examines all the messages between the initiator and target and provides SCSI flow features, such as Fibre Channel write acceleration and statistics monitoring.
Note |
The SCSI target and initiator must be connected to different SSMs on different switches. |
Note |
For statistics monitoring, the target device is not required to be connected to an SSM. |
SCSI Flow Manager
The SCSI flow manager (SFM) resides on a supervisor module and handles the configuration of SCSI flows, validating them and relaying configuration information to the appropriate SSM. It also handles any dynamic changes to the status of the SCSI flow due to external events. The SFM registers events resulting from operations, such as port up or down, VSAN suspension, and zoning that affects the SCSI flow status, and updates the flow status and configuration accordingly.
The SFM on the initiator communicates to its peer on the target side using Cisco Fabric Services (CFS). Peer communication allows the initiator SFM to validate target parameters and program information on the target side.
SCSI Flow Configuration Client
A SCSI flow configuration client (SFCC) resides on the CPP of the SSM. It receives flow configuration requests from the SFM, programs the DPP corresponding to the initiator and target port interfaces, and responds to the SFM with the status of the configuration request.
SCSI Flow Data Path Support
The DPP on the SSM examines all the messages between the initiator and target and provides SCSI flow features such as Fibre Channel write acceleration and statistics monitoring.
SCSI Flow Services Configuration
A SCSI flow specification consists of the following attributes:
- SCSI flow identifier
- VSAN identifier
- SCSI initiator port WWN
- SCSI target port WWN
- Flow feature set consisting of Fibre Channel Write Acceleration and statistics monitoring.
The SCSI flow specification is a distributed configuration because the SCSI initiator and the target might be physically connected to SSMs on two different switches located across the fabric. The configuration does not require information to identify either the switch name or the SSM slot location for either the initiator or the target. The manual SCSI flow configuration is performed only at the initiator side. This simplifies the configuration process. The initiator switch sends the configuration to the SFM on the target switch using CFS. No SCSI flow configuration is necessary on the target switch.
About Intelligent Storage Services
Intelligent Storage Services are features supported on the Storage Services Module (SSM). Intelligent Storage Services supported in Cisco MDS SAN-OS Release 2.0(2b) and later, or Cisco NX-OS 4.1.(1) include the following:
- SCSI flow services
- SCSI flow statistics
In Cisco MDS SAN-OS Release 2.1(1a) or later, or Cisco NX-OS 4.1(1), you can provision a subset of the ports for an SSM feature. The port range must be a multiple of four (for example fc4/1 through fc4-12).You can enable SCSI flow services either on the entire SSM or on groups of four interfaces.
Enabling SCSI flow services on interfaces has the following restrictions:
- The fewest number of interfaces that you can enable is four. You can specify fc1 through fc4, but not fc1 through fc2.
- The first interface in the group must be 1, 5, 9, 13, 17, 21, 25, or 29. You can specify fc5 through fc8, but not fc7 through fc10.
- The groups of four interfaces do not need to be consecutive. You can specify fc1 through fc8 and fc17 through fc20.
Note |
Fibre Channel Write Acceleration can only be provisioned on the entire SSM, not a group of interfaces on the SSM. |
Enabling SCSI Flow Services
SUMMARY STEPS
- switch# config t
- switch(config)# ssm enable feature scsi-flow module 2
- switch(config)# no ssm enable feature scsi-flow module 2
- switch(config)# no ssm enable feature scsi-flow force module 2
- switch(config)# ssm enable feature scsi-flow interface fc 2/5 - 8
- switch(config)# no ssm enable feature scsi-flow interface fc 2/5 - 8
- switch(config)# no ssm enable feature scsi-flow force interface fc 2/5 - 8
DETAILED STEPS
Command or Action | Purpose | |||
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Step 1 |
switch# config t Example:
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Enters configuration mode. |
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Step 2 |
switch(config)# ssm enable feature scsi-flow module 2 |
Enables SCSI flow services on the SSM in slot 2. |
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Step 3 |
switch(config)# no ssm enable feature scsi-flow module 2 |
Disables SCSI flow services on the SSM in slot 2. The default is disabled. |
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Step 4 |
switch(config)# no ssm enable feature scsi-flow force module 2 |
Forces the switch to disable SCSI flow services on the SSM in slot 2. The default is disabled. |
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Step 5 |
switch(config)# ssm enable feature scsi-flow interface fc 2/5 - 8 |
Enables SCSI flow services on interface 5 through 8 on the SSM in slot 2.
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Step 6 |
switch(config)# no ssm enable feature scsi-flow interface fc 2/5 - 8 |
Disables SCSI flow services on interface 5 through 8 on the SSM in slot 2. The default is disabled. |
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Step 7 |
switch(config)# no ssm enable feature scsi-flow force interface fc 2/5 - 8 |
Forces the switch to disable SCSI flow services on the interface 5 through 8 on the SSM in slot 2. |
Enabling SCSI Flow Configuration Distribution
To enable SCSI flow configuration distribution using CFS, follow these steps:
SUMMARY STEPS
- switch# config t
- switch(config)# scsi-flow distribute
- switch(config)# no scsi-flow distribute
DETAILED STEPS
Command or Action | Purpose | |
---|---|---|
Step 1 |
switch# config t Example:
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Enters configuration mode. |
Step 2 |
switch(config)# scsi-flow distribute |
Enables SCSI flow configuration distribution through CFS. The default is enabled. |
Step 3 |
switch(config)# no scsi-flow distribute |
Disables CFS distribution for SCSI flow configuration. |
Configuring SCSI Flow Identifiers
A SCSI flow identifier is unique on a switch such as VSAN identifiers and is chosen by the user. To configure a SCSI flow identifier, follow these steps:
SUMMARY STEPS
- switch# config t
- switch(config)# scsi-flow flow-id 3 initiator-vsan 2 initiator-pwwn 21:00:00:e0:8b:07:5f:aa target-vsan 4 target-pwwn 2a:20:00:05:30:00:77:e0
- switch(config)# no scsi-flow flow-id 3 initiator-vsan 2
DETAILED STEPS
Command or Action | Purpose | |
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Step 1 |
switch# config t Example:
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Enters configuration mode. |
Step 2 |
switch(config)# scsi-flow flow-id 3 initiator-vsan 2 initiator-pwwn 21:00:00:e0:8b:07:5f:aa target-vsan 4 target-pwwn 2a:20:00:05:30:00:77:e0 |
Configures SCSI flow identifier 3 using the pWWNs of the initiator and the target. The flow identifier range is 1 to 65535. |
Step 3 |
switch(config)# no scsi-flow flow-id 3 initiator-vsan 2 |
Removes SCSI flow identifier 3. |