102 lines
7.2 KiB
HTML
102 lines
7.2 KiB
HTML
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html
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PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html lang="en-us" xml:lang="en-us">
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<meta name="DC.Type" content="concept" />
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<meta name="DC.Title" content="Disk" />
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<meta name="abstract" content="This topic describes how disk storage on the iSeries works and describes how it can be configured and used for different storage purposes." />
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<meta name="description" content="This topic describes how disk storage on the iSeries works and describes how it can be configured and used for different storage purposes." />
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<meta name="DC.Relation" scheme="URI" content="http://www.ibm.com/servers/eserver/iseries/hsmcomp/index.html" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 2004, 2006" />
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<meta name="DC.Identifier" content="rzam4disk" />
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<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
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<link rel="stylesheet" type="text/css" href="./ic.css" />
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<title>Disk</title>
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</head>
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<body id="rzam4disk"><a name="rzam4disk"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Disk</h1>
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<div><p>This topic describes how disk storage on the iSeries™ works
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and describes how it can be configured and used for different storage purposes.</p>
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<p>Disk storage is the storage that is usually internal to your iSeries server;
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however, it can also be attached externally to it. You can group your disk
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drives into logical subsets called <dfn class="term">disk pools</dfn> (also known as
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auxiliary storage pools or ASPs). One reason to do this is to provide a level
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of protection for your data. If one disk unit fails, you only have to recover
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the data stored in the disk pool that the failed disk unit was a part of.</p>
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<p>Disk pools also enable you to set disk space aside for a particular purpose,
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application, or data type. For example, you may create a disk pool for backups
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done to save files. You can then move these save files to tape or other media
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when it is convenient for you. The following diagram shows a disk pool that
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is composed of disk units 1, 4, 5, 7, and 11.</p>
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<br /><img src="rzam4502.gif" alt="A disk pool on the iSeries server" /><br /><p>For detailed information about disk pools, disk pool types, and examples
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of how to use disk pools for different purposes, see Disk pools. For information
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about how to configure disk units and disk pools, see Manage disk pools.</p>
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<p><dfn class="term">Independent disk pools</dfn> are disk pools that can be brought
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online or taken offline without any dependencies on the rest of the storage
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on a system. This is possible because all of the necessary system information
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associated with the independent disk pool is contained within the independent
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disk pool. Independent disk pools offer a number of availability and performance
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advantages in both single and multiple system environments. For detailed information,
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see Using independent disk pools.</p>
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<p>Besides disk pools, there are a few other ways to protect your disk units
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and the data on them. <dfn class="term">Mirrored protection</dfn> protects your data
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by keeping a copy of the data on two separate disk units. When a disk-related
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component fails, the system may continue to operate without interruption by
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using the mirrored copy of the data until the failed component is repaired.
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<dfn class="term">Device parity protection</dfn> is a hardware function that enables
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your server to reconstruct data in the event of a disk failure. It is important
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to remember that these disk protection methods are not a guarantee against
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failure or data loss. You still need to have a good backup and recovery strategy
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in place in order to truly protect your data. For detailed information about
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the disk protection methods described here, see Plan for disk protection.</p>
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<p>Compared to tape or optical, disk is a more expensive storage option. However,
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the data on disk is more quickly accessible than on tape or optical. It is
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important to balance the cost of storing data on disk with the speed and convenience
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with which you can access that data. For example, if you have older data that
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you access infrequently, you may want to consider storing it on tape or optical,
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rather than on disk. Likewise, current information that you access frequently
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might be worth the cost of disk storage because you can access it quickly.
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This type of storage strategy is called <dfn class="term">hierarchical storage management</dfn>.
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The following diagram shows the different layers of hierarchical storage management:</p>
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<br /><img src="rzam4503.gif" alt="Hierarchical storage management" /><br /><p>It is not always the same data that resides in the high performance storage
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components. Data is moved among the different layers according to the current
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system needs. The key to successful and seamless hierarchical storage management
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lies in the management and distribution of data across the different layers.
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For detailed information, see Hierarchical Storage Management.</p>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rzam4overview.htm" title="As your company produces a greater volume of information, and as the value of that information grows, the methods you use to protect and preserve it become vital corporate strategies. Storage has gone from being a feature of a server to being an entity unto itself.">Storage solutions</a></div>
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</div>
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<div class="relconcepts"><strong>Related concepts</strong><br />
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<div><a href="../rzaly/rzalyaspsovrvw.htm">Disk pools</a></div>
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<div><a href="../rzaly/rzalyoverview.htm">Using independent disk pools</a></div>
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<div><a href="../rzaly/rzalyprtctvsdtalss.htm">Plan for disk protection</a></div>
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</div>
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<div class="reltasks"><strong>Related tasks</strong><br />
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<div><a href="../rzaly/rzalyoptimize.htm">Manage disk pools</a></div>
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</div>
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<div class="relinfo"><strong>Related information</strong><br />
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<div><a href="http://www.ibm.com/servers/eserver/iseries/hsmcomp/index.html" target="_blank">Hierarchical storage management</a></div>
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</div>
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</div>
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</body>
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</html>
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