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This chapter describes the Fibre Channel Write Acceleration (FC-WA) feature, including how to enable the feature on Cisco NX-OS.
Fibre Channel Write Acceleration minimizes application latency or reduces transactions per second over long distances. For synchronous data replication, Fibre Channel Write Acceleration increases the distance of replication or reduces effective latency to improve performance. With this feature you can also configure the buffer count and change the number of 2-KB buffers reserved on the target side DPP for a SCSI flow.
To take advantage of this feature, both the initiator and target devices must be directly attached to an SSM.
The Fibre Channel Write Acceleration feature also allows the configuration of the buffer count. You can change the number of 2-KB buffers reserved on the target side DPP for a SCSI flow.
You can estimate the number of buffers to configure using the following formula:
(Number of concurrent SCSI writes * size of SCSI writes in bytes) / FCP data frame size in bytes
For example, HDS TrueCopy between HDS 9970s uses 1-KB FCP data frames. You perform an initial synchronization for a 16-LUN TrueCopy group with 15 tracks, or 768-KB per LUN, which requires approximately 16*(768*1024)/1024 or 12248 write buffers.
Note The Fibre Channel Write Acceleration feature requires the Enterprise Package license installed on both the initiator and target switches.
Note The initiator and target cannot connect to the same Cisco MDS switch. Fibre Channel Write Acceleration requires that the initiator and target must each connect to an SSM module installed on different Cisco MDS switches.
Note Fibre Channel Write Acceleration can only be provisioned on the entire SSM, not a group of interfaces on the SSM.
The following table shows the licensing requirements for Fibre Channel Write Acceleration:
Table 4-1 lists the default settings for Fibre Channel Write Acceleration parameters.
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This section includes the following topics:
To enable Fibre Channel Write Acceleration, and optionally modify the number of Write Acceleration buffers using the DCNM-SAN, follow these steps:
Step 1 Expand End Devices and then select S SM Features from the Physical Attributes pane.
You see the Intelligent Storage Services configuration, showing the FCWA tab in the Information pane.
Step 2 Click Create Row in the Information pane to create a SCSI flow or click a row in the FCWA table to modify an existing SCSI flow.
You see the FC Write Acceleration dialog box.
Step 3 Select the initiator and target WWNs and VSAN IDs and check the WriteAcc check box to enable Fibre Channel Write Acceleration on this SCSI flow.
Step 4 (Optional) Enable SCSI flow statistics on this SCSI flow at this time by checking the Enable Statistics check box.
Step 5 (Optional) Set the BufCount value to the number of 2K buffers used by the SCSI target.
Step 6 Click Create to create this SCSI flow with Fibre Channel Write Acceleration.
To display Fibre Channel Acceleration configuration information, perform one of the following tasks:
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Displays Fibre Channel Write Acceleration configuration for all SCSI flow identifiers. |
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Displays Fibre Channel Write Acceleration configuration for a specific SCSI flow identifiers. |
For detailed information about the fields in the output from these commands, refer to the Cisco DC-OS Command Reference.
This section includes the following topics:
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If false, it’s the data path. If true, it’s the control path. |