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    <title>FCIP Write Acceleration </title>
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<a name="wp1076802"> </a><h1 class="pTitle">
FCIP Write Acceleration

</h1>
<a name="wp1076803"> </a><p class="pBody">
The FCIP write acceleration feature enables you to significantly improve application write performance 
when storage traffic is routed over wide area networks using FCIP. When FCIP write acceleration is 
enabled, WAN throughput is maximized by minimizing the impact of WAN latency for write operations.

</p>
<a name="wp1076804"> </a><p class="pBodyAutonumNoRule">
<strong>Note	&nbsp;&nbsp;&nbsp;</strong> The write acceleration feature is disabled by default and must be enabled on both sides of the FCIP link. 
If it is only enabled on one side of the FCIP tunnel the write acceleration feature will be turned 
operationally off.

</p>
<a name="wp1076805"> </a><p class="pBodyAutonumNoRule">
<strong>Note	&nbsp;&nbsp;&nbsp;</strong> IBM Peer to Peer Remote Copy (PPRC) is not supported with FCIP write acceleration.

</p>
<a name="wp1076809"> </a><p class="pBody">
The WRITE command ,without write acceleration requires two round-trip transfers (RTT), while the 
WRITE command with write acceleration only requires one RTT. The maximum sized Transfer Ready 
is sent from the host side of the FCIP link back to the host before the WRITE command reaches the 
target. This enables the host to start sending the write data without waiting for the long latency over the 
FCIP link of the WRITE command and Transfer Ready. It also eliminates the delay caused by multiple 
Transfer Readys needed for the exchange going over the FCIP link.

</p>
<a name="wp1076816"> </a><p class="pBodyAutonumRel">
<strong>Tip	&nbsp;&nbsp;&nbsp;</strong> FCIP write acceleration can be enabled for multiple FCIP tunnels if the tunnels are part of a dynamic 
PortChannel configured with channel mode active. FCIP write acceleration does not work if multiple 
non-PortChannel ISLs exist with equal weight between the initiator and the target port. Such a 
configuration might cause either SCSI discovery failure or failed WRITE or READ operations. 

</p>
<a name="wp1076817"> </a><p class="pBodyAutonumRel">
<strong>Tip	&nbsp;&nbsp;&nbsp;</strong> Do not enable time stamp control on an FCIP interface with write acceleration configured.

</p>
<a name="wp1076818"> </a><p class="pBodyAutonumNoRule">
<strong>Note	&nbsp;&nbsp;&nbsp;</strong> Write acceleration cannot be used across FSPF equal cost paths in FCIP deployments. Native Fibre 
Channel write acceleration can be used with PortChannels. Also, FCIP write acceleration can be used in 
PortChannels configured with channel mode active or constructed with PortChannel Protocol (PCP).

</p>
<a name="wp1076819"> </a><p class="pCaution">
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<td>
<strong>Caution	&nbsp;&nbsp;&nbsp;</strong>
</td>
<td>
<p>In Cisco MDS SAN-OS Release 2.0(1b) and later and NX-OS Release 4.x, FCIP write acceleration with 
FCIP ports as members of PortChannels are not compatible with the FCIP write acceleration in earlier 
releases.
</p>
</td>
</tr>
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</p>
<hr /><br><p class="pBody">Copyright 2010-2013, Cisco Systems, Inc. All rights reserved.</p> 

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