<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<!-- saved from url=(0014)about:internet -->
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
    <meta http-equiv="Content-Style-Type" content="text/css" />
    <meta name="GENERATOR" content="Quadralay WebWorks AutoMap 2003 Platinum Edition Client for FrameMaker 8.6.6597.0" />
    <meta name="TEMPLATEBASE" content="emwebh8-1-17" />
    <meta name="LASTUPDATED" content="08/01/13 14:47:30" />
    <title>Information About SDV </title>
    <!-- Copyright 2010-2013, Cisco Systems, Inc. All rights reserved. -->

    <link rel="StyleSheet" href="document.css" type="text/css" />
    <link rel="StyleSheet" href="catalog.css" type="text/css" />


<script> 
    var is_chrome = navigator.userAgent.toLowerCase().indexOf('chrome') > -1; 
   
    if(is_chrome){document.domain=document.domain}
   </script>
    <script type="text/javascript" language="JavaScript1.2" src="expand.js"></script>
    <script type="text/javascript" language="JavaScript1.2" src="page.js"></script>

    <script type="text/javascript" language="JavaScript1.2">
     <!--
      function  WWNoOp() {}
      function  WWNoValue() { return ""; }

      var  VarDropDown;

      if (typeof(HTMLHelp_Object) != "undefined")
      {
        VarDropDown = new WWDropDown_Object();
      }
      else
      {
        VarDropDown = new Object();
        VarDropDown.fAnchorOpen  = WWNoOp;
        VarDropDown.fAnchorClose = WWNoOp;
        VarDropDown.fDIVOpen  = WWNoOp;
        VarDropDown.fDIVClose = WWNoOp;
      }
     // -->
    </script>

  
<SCRIPT language="javascript">
<!--
  self.document.write("<link href='"+top.relPath+"shared/style.css' rel='stylesheet' type='text/css'>");
  myid=1194;
  self.document.write("<script type='text/javascript' language='JavaScript' src='"+top.relPath+"shared/con_utils.js'></scr"+"ipt>");
//-->
</SCRIPT>
</head>

  <body onload="highlightSearchTerms();" bgcolor="#ffffff">

    
    <blockquote>
    <a name="top"></a>

    
    


<a name="wp1072707"> </a><h1 class="pTitle">
Information About SDV

</h1>
<a name="wp1072708"> </a><p class="pBody">
As of Cisco SAN-OS Release 3.1(2) and later, you can use Cisco SAN device virtualization to create 
virtual devices that represent physical end-devices. Virtualization of SAN devices accelerates swapout 
or failover to a replacement disk array, and it also minimizes downtime when replacing host bus adapters 
(HBAs) or when rehosting an application on a different server.

</p>
<a name="wp1072541"> </a><p class="pBody">
SAN device virtualization enables you to:

</p>
<div class="pSmartList1"><ul class="pSmartList1">
<a name="wp1072542"> </a><li class="pSmartList1">Reduce the amount of time it takes for data migration, and ultimately the overall amount of 
downtime.
</li>
<a name="wp1072543"> </a><li class="pSmartList1">Improve ease-of-use and reduce the possibility of user-introduced errors during the failover by 
performing the operation in a single step.
</li>
<a name="wp1072544"> </a><li class="pSmartList1">Easily scale to larger numbers of targets.
</li>
</ul></div>
<a name="wp1072545"> </a><p class="pBody">
SAN devices that are virtualized can be either initiators or targets. You can virtualize targets to create a 
<em class="cEmphasis">virtual target</em> and also virtualize initiators to create a <em class="cEmphasis">virtual initiator</em>. SAN device configurations do not 
distinguish between virtual initiators and virtual targets .

</p>
<a name="wp1072558"> </a><p class="pBodyRelative">

</p>
<a name="wp1072565"> </a><p class="pBodyAutonumNoRule">
<strong>Note	&nbsp;&nbsp;&nbsp;</strong> While most of the examples in this chapter describe target virtualization, the initiator virtualization 
functions similarly.

</p>
<a name="wp1072566"> </a><p class="pBody">
Typically, today’s deployments for handling device failures are designed for high availability (HA), with 
redundancy being a key part of this design. Consider the situation where a target is designed to be 
redundant. Two arrays are deployed–a primary and secondary in this situation. Enterprises often use 
some type of consistency technology (such as EMF SRDF) between the primary and secondary arrays 
to ensure that the secondary is a mirrored copy of the production LUN. However, if the primary array 
fails, it must be replaced by the secondary because all I/O must occur on the secondary array. Problems 
can occur because the time required to bring the secondary array up and have it working often takes 
longer than most can afford.

</p>
<a name="wp1072576"> </a><p class="pBody">
If a storage array is replaced <span style="font-style: italic">without</span> using Cisco SDV, then it may require the following actions:

</p>
<div class="pSmartList1"><ul class="pSmartList1">
<a name="wp1072577"> </a><li class="pSmartList1">Taking down a server to modify zoning and account for the new array.
</li>
<a name="wp1072578"> </a><li class="pSmartList1">Changing the Cisco NX-OS configuration to accommodate Fibre Channel IDs (FC IDs) and 
pWWNs of the new array.
</li>
<a name="wp1072579"> </a><li class="pSmartList1">Changing a server configuration to accommodate the new FC IDs and pWWNs.
</li>
</ul></div>
<a name="wp1072580"> </a><p class="pBody">
More specifically, without SDV you might experience the following conditions:

</p>
<div class="pSmartList1"><ul class="pSmartList1">
<a name="wp1072581"> </a><li class="pSmartList1">It can take a considerable amount of time to configure a secondary device for a typical production 
environment.
</li>
<a name="wp1072582"> </a><li class="pSmartList1">In the zoning configuration, all the initiators must be rezoned with the secondary device, and certain 
initiators must also be reconfigured. For example, the WWN and FC ID of the secondary device are 
different, so driver files must be changed and the server must be rebooted.
</li>
<a name="wp1072583"> </a><li class="pSmartList1">Clustering (multiple initiators) compounds the problem, and the failover procedure must be repeated 
for each server of the cluster. Think of a server cluster as a set of HBAs–any storage array FC ID 
changes must be performed for each HBA.
</li>
</ul></div>
<a name="wp1072584"> </a><p class="pBody">
SDV enables you to achieve the following performance targets:

</p>
<div class="pSmartList1"><ul class="pSmartList1">
<a name="wp1072585"> </a><li class="pSmartList1">Reduce the amount of time it takes for data migration, and ultimately the overall amount of 
downtime.
</li>
<a name="wp1072586"> </a><li class="pSmartList1">Easily scale to larger numbers of devices.
</li>
</ul></div>
<a name="wp1072590"> </a><p class="pBody">
When disk array X was deployed, the user created virtual devices for all the Fibre Channel interfaces 
using SDV. After data replication from disk array X was completed, the user briefly pauses activity on 
the application server and relinked disk array Y to the virtual devices used by the server, completing the 
swapout of disk array X. No zoning changes or host operating system configuration changes were 
required during the time-critical period when the swap was performed; this significantly minimized 
application downtime.

</p>
<a name="wp1072591"> </a><p class="pBodyAutonumNoRule">
<strong>Note	&nbsp;&nbsp;&nbsp;</strong> The array administrator will likely have to perform actions on array Y for it to become a primary device 
and accept server logins before linking the virtual device to the array Y pWWN.

</p>
<a name="wp1072598"> </a><p class="pBody">
This section includes the following topics:

</p>
<div class="pSmartList1"><ul class="pSmartList1">
<a name="wp1075531"> </a><li class="pSmartList1"><a href="sandv03.html">Key Concepts</a>
</li>
<a name="wp1075542"> </a><li class="pSmartList1"><a href="sandv04.html">Automatic Failover and Fallback</a>
</li>
<a name="wp1075543"> </a><li class="pSmartList1"><a href="sandv05.html">Resolving Fabric Merge Conflicts</a>
</li>
</ul></div>
<hr /><br><p class="pBody">Copyright 2010-2013, Cisco Systems, Inc. All rights reserved.</p> 

    </blockquote>

  </body>
</html>
