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    <title>Information About Fibre Channel Write Acceleration </title>
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<a name="wp1167012"> </a><h1 class="pTitle">
Information About Fibre Channel Write Acceleration

</h1>
<a name="wp1167013"> </a><p class="pBody">
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.

</p>
<a name="wp1167014"> </a><p class="pBody">
To take advantage of this feature, both the initiator and target devices must be directly attached to an 
SSM.

</p>
<a name="wp1167015"> </a><p class="pBody">
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.

</p>
<a name="wp1167017"> </a><p class="pBody">
You can estimate the number of buffers to configure using the following formula:

</p>
<a name="wp1167018"> </a><p class="pBody">
(Number of concurrent SCSI writes * size of SCSI writes in bytes) / FCP data frame size in bytes

</p>
<a name="wp1167019"> </a><p class="pBody">
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.

</p>
<a name="wp1167021"> </a><p class="pBodyAutonumNoRule">
<strong>Note	&nbsp;&nbsp;&nbsp;</strong> The Fibre Channel Write Acceleration feature requires the Enterprise Package license installed on both 
the initiator and target switches.

</p>
<a name="wp1167022"> </a><p class="pBodyAutonumNoRule">
<strong>Note	&nbsp;&nbsp;&nbsp;</strong> 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. 

</p>
<a name="wp1170967"> </a><p class="pBodyAutonumNoRule">
<strong>Note	&nbsp;&nbsp;&nbsp;</strong> Fibre Channel Write Acceleration can only be provisioned on the entire SSM, not a group of interfaces 
on the SSM.

</p>
<hr /><br><p class="pBody">Copyright 2010-2013, Cisco Systems, Inc. All rights reserved.</p> 

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