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.

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.

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.

The statistics that can be collected for SCSI flows include the following:

• SCSI reads
  • Number of I/Os
  • Number of I/O blocks
  • Maximum I/O blocks
  • Minimum I/O response time
  • Maximum I/O response time
• SCSI writes
  • Number of I/Os
  • Number of I/O blocks
  • Maximum I/O blocks
  • Minimum I/O response time
  • Maximum I/O response time
• Other SCSI commands (not read or write)
  • Test unit ready
  • Report LUN
  • Inquiry
  • Read capacity
  • Mode sense
  • Request sense
• Errors
  • Number of timeouts
  • Number of I/O failures
  • Number of various SCSI status events
  • Number of various SCSI sense key errors or events

To take advantage of this feature, only the initiator must be directly attached to an SSM

Note	The SCSI flow statistics feature requires the Enterprise Package license installed only on the initiator switches.

Note	For SCSI flow statistics, the initiator must connect to an SSM on a Cisco MDS switch while the target can connect to any other switch in the fabric. The SCSI flow initiator and target cannot connect to the same switch.

This section includes the following topics: