The documentation set for this product strives to use bias-free language. For the purposes of this documentation set, bias-free is defined as language that does not imply discrimination based on age, disability, gender, racial identity, ethnic identity, sexual orientation, socioeconomic status, and intersectionality. Exceptions may be present in the documentation due to language that is hardcoded in the user interfaces of the product software, language used based on RFP documentation, or language that is used by a referenced third-party product. Learn more about how Cisco is using Inclusive Language.
This chapter describes the Fibre Channel Write Acceleration(FC-WA) feature, including how to enable the feature on Cisco NX-OS.
This chapter includes the following sections:
•About Fibre Channel Write Acceleration
•Enabling Fibre Channel Write Acceleration
•Displaying Fibre Channel Write Acceleration Information
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.
To enable Fibre Channel Write Acceleration, and optionally modify the number of write acceleration buffers, follow these steps:
Use the show scsi-flow command to display information about the status of the Fibre Channel write acceleration configuration (see Example 3-1 and Example 3-2).
Example 3-1 Displays Fibre Channel Write Acceleration Configuration for All SCSI Flow Identifiers
switch# show scsi-flow
Flow Id: 3
Initiator VSAN: 101
Initiator WWN: 21:00:00:e0:8b:05:76:28
Target VSAN: 102
Target WWN: 21:00:00:20:37:38:7f:7d
Target LUN: ALL LUNs
Flow Verification Status:
-------------------------
Initiator Verification Status: success
Target Verification Status: success
Initiator Linecard Status: success
Target Linecard Status: success
Feature Status:
---------------
Write-Acceleration enabled
Write-Acceleration Buffers: 1024
Configuration Status: success
Statistics enabled
Configuration Status: success
Flow Id: 4
Initiator VSAN: 101
Initiator WWN: 21:00:00:e0:8b:05:76:28
Target VSAN: 102
Target WWN: 21:00:00:20:37:38:a7:89
Target LUN: ALL LUNs
Flow Verification Status:
-------------------------
Initiator Verification Status: success
Target Verification Status: success
Initiator Linecard Status: success
Target Linecard Status: success
Feature Status:
---------------
Write-Acceleration enabled
Write-Acceleration Buffers: 1024
Configuration Status: success
Statistics enabled
Configuration Status: success
Example 3-2 Displays Fibre Channel Write Acceleration Configuration for a Specific SCSI Flow Identifier
switch# show scsi-flow flow-id 3
Flow Id: 3
Initiator VSAN: 101
Initiator WWN: 21:00:00:e0:8b:05:76:28
Target VSAN: 102
Target WWN: 21:00:00:20:37:38:7f:7d
Target LUN: ALL LUNs
Flow Verification Status:
-------------------------
Initiator Verification Status: success
Target Verification Status: success
Initiator Linecard Status: success
Target Linecard Status: success
Feature Status:
---------------
Write-Acceleration enabled
Write-Acceleration Buffers: 1024
Configuration Status: success
Statistics enabled
Configuration Status: success
Table 3-1 lists the default settings for Fibre Channel write acceleration parameters.
|
|
---|---|
Fibre Channel write acceleration |
Disabled |
Fibre Channel write acceleration buffers |
1024 |