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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.
This chapter includes the following sections:
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. |
Command or Action | Purpose | |||
---|---|---|---|---|
Step 1 |
switch# config t Example: switch(config)# |
Enters configuration mode. | ||
Step 2 | switch(config)# ssm enable feature scsi-flow module 2 |
Enables SCSI flow services on the SSM in slot 2.
| ||
Step 3 | 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 4 | switch(config)# scsi-flow distribute |
Enables CFS distribution for the SCSI flow.
| ||
Step 5 | switch(config)# scsi-flow flow-id 3 write-acceleration |
Enables Fibre Channel write acceleration for SCSI flow identifier 3. | ||
Step 6 | switch(config)# no scsi-flow flow-id 3 write-acceleration |
Disables SCSI flow write acceleration for SCSI flow identifier 3. The default is disabled. | ||
Step 7 | switch(config)# scsi-flow flow-id 3 write-acceleration buffer 2048 |
Enables Fibre Channel write acceleration for SCSI flow identifier 3 and sets the number of buffers to 2048. The range is 1 to 40000. | ||
Step 8 | switch(config)# no scsi-flow flow-id 3 write-acceleration buffer 1024 |
Reverts to the default number of write acceleration buffers. The default is 1024. |
Use the show scsi-flow command to display information about the status of the Fibre Channel write acceleration configuration.
The following example 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
The following example 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 1 lists the default settings for Fibre Channel write acceleration parameters.
Parameters |
Default |
---|---|
Fibre Channel write acceleration |
Disabled |
Fibre Channel write acceleration buffers |
1024 |