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S e n d d o c u m e n t a t i o n c o m m e n t s t o m d s f e e d b a c k - d o c @ c i s c o . c o m .
Configuring Fibre Channel Write Acceleration
The Storage Services Module (SSM) supports Intelligent Storage Services in Cisco MDS SAN-OS
Release 2.0(2b) and later that include Fibre Channel write acceleration.
This chapter includes the following sections:
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About Fibre Channel Write Acceleration
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. 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, for HDS TrueCopy between HDS 9970s, which use 1KB FCP data frames, and you perform
an initial sync for a 16-LUN TrueCopy group with 15 tracks, or 768 KB per LUN, the approximate
number of write buffers required would be 16*(768*1024)/1024 or 12248 buffers.
Note
The Fibre Channel write acceleration feature requires the Enterprise Package license installed on both
the initiator and target switches.
The initiator and target cannot connect to the same Cisco MDS switch. Fibre Channel write acceleration
Note
requires that the negotiator and target must each connect to an SSM module installed on different Cisco
MDS switches.
OL-6973-03, Cisco MDS SAN-OS Release 2.x
About Fibre Channel Write Acceleration, page 39-1
Enabling Fibre Channel Write Acceleration, page 39-2
Displaying SCSI Flow Services Information, page 39-2
Default Settings, page 39-3
C H A P T E R
Cisco MDS 9000 Family Configuration Guide
39
39-1
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