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<h1 class="topictitle1">Choose dedicated or switchable IOP and devices for logical partitions</h1>
<div><p>Use this information to determine if dedicated or switchable IOP
are right for your partitioned environment.</p>
<p>IOPs that are candidates for switching include:</p>
<ul><li>IOPs that control high cost devices.</li>
<li>IOPs that control low utilization devices and low demand devices.</li>
<li>IOPs that solely control the target device or devices.</li>
</ul>
<p>The IBM<sup>®</sup> recommended
approach is to confine all hardware within a partition. This is not always
a cost-effective solution. With some devices it may be preferable to share
them among partitions. Although partitions do not support concurrent device
sharing, IOP-level switching may be an effective solution.</p>
<ul><li><strong>Advantages of switching IOPs and devices</strong><ul><li>Reduced cost.</li>
<li>Fewer card positions needed. In some cases, this could mean that you need
fewer expansion units.</li>
</ul>
</li>
<li> <strong>Disadvantages of switching IOPs and devices</strong><ul><li>Inconvenience of having to schedule use of switchable IOPs and devices.</li>
</ul>
</li>
</ul>
<div class="attention"><span class="attentiontitle">Attention:</span> For external tape (for instance, 3590), it is possible
to have one tape device, but separate IOPs for each partition that will use
it. A partition requesting use of the device receives a "busy" indication
if it is in use by another partition.</div>
<p>Before implementing a switchable IOP and other devices, you should also
consider other possible alternatives. To share devices among partitions, you
can apply the same techniques that are used to share devices among separate
physical servers:</p>
<ul><li>Use multiple IOPs, one in each partition, for devices that support multiple
connections (some high end tape drives).</li>
<li>Use multiple IOPs, one in each partition and use a switch box for devices
that only support single connections (printers, or some high end tape drives).</li>
<li>Use multiple IOPs and multiple devices in each partition for a self-contained
solution (internal removable media devices).</li>
</ul>
</div>
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<div class="familylinks">
<div class="parentlink"><strong>Parent topic:</strong> <a href="rzaitunderstandhardware.htm" title="Determine if your hardware resources meet the minimum requirements needed to partition your server. Evaluate each iSeries model to determine how your hardware will function once you partition your server.">Hardware requirements for logical partitions</a></div>
</div>
<div class="relconcepts"><strong>Related concepts</strong><br />
<div><a href="rzaitchoosebusiop.htm" title="Depending on your needs, there can be advantages to partitioning your I/O resources in different ways.">Select bus-level or IOP-level partitioning</a></div>
</div>
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