111 lines
6.6 KiB
HTML
111 lines
6.6 KiB
HTML
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<meta name="DC.Title" content="Copy Optical (CPYOPT) performance" />
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<meta name="abstract" content="Performance is a complex subject with many interdependent components." />
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<title>Copy Optical (CPYOPT) performance</title>
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<body id="rzam4copyoptperf"><a name="rzam4copyoptperf"><!-- --></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">Copy Optical (CPYOPT) performance</h1>
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<div><p>Performance is a complex subject with many interdependent components.</p>
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<p>By changing one component, you may adversely affect another. This interdependence
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and the other factors that affect performance, prohibits providing a formula
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for computing the time required to copy a given number of files. It is simply
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a guideline to help you estimate how long your CPYOPT might take. </p>
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<p>You may need to estimate how long it takes to copy an entire optical volume
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when using the CPYOPT command. You can start by copying a single directory
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that contains a known number of average sized files. Then take the difference
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between the ending time and starting time to determine an elapsed time. Take
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the elapsed time and divide by the number of files that are copied to figure
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the average seconds per file. You can use this number as a basis to determine
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the amount of time that is required to copy the entire volume of average size
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files.</p>
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<p>To maximize copy performance, use the following set of guidelines as a
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starting point:</p>
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<ul><li>Having too few directories with too many files can affect performance.
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Having too many directories with too few files can affect performance also.
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Try to keep the number of files in a directory to less than 6000 files.</li>
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<li>Consider performance when determining file size.</li>
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<li>Avoid use of extended attributes on files. When a file has extended attributes,
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they are storied separately from the data. When copying the data, the must
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copy the attributes also. It is similar to copying a second file for each
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user file copied.</li>
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<li>Keep the source and target volumes in the same library.</li>
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<li>Avoid copying to the opposite side of an optical cartridge.</li>
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<li>If the copy processes can have dedicated use of the optical drives, use
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the COPYTYPE *IOP parameter on the CPYOPT command.</li>
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<li>Avoid optical drive contention from other optical processes.</li>
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<li>Dedicate the use of two optical drives for copy activity.</li>
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</ul>
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<p> </p>
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<div class="section"><h4 class="sectiontitle">Drive contention</h4><p>The following conditions can severely
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affect copy performance:</p>
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<ul><li>Having only one drive available for use.</li>
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<li>Copying from one side of an optical cartridge to the opposite side.</li>
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<li>Having other optical processes that are running that attempt to use the
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available drives.</li>
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<li>A large number of files on source volume.</li>
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</ul>
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<p> To remove a volume, to store it in a slot, to retrieve a new volume,
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and to mount it requires from 8-15 seconds.</p>
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<p> You should try to do your
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copy requests when the process can have dedicated use of the optical drives.
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You should not try to copy a large number of files from one side of an optical
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cartridge to the other side. Optical drives have only one read/write head.
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The following conditions occur when copying from one side of an optical cartridge
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to another:</p>
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<ul><li>The system mounts the source volume.</li>
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<li>A limited number of files that are to be copied are read and stored on i5/OS™ temporary
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storage.</li>
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<li>The source volume is removed, and the system mounts the target volume
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by turning over the optical cartridge.</li>
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<li>Files are read from i5/OS temporary storage and written to the target volume.</li>
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<li>If there are more files to copy, the system removes target volume and
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mounts the source volume again by turning over the optical cartridge.</li>
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<li>The system repeats this process until it copies all the files. You may
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need to turn the optical cartridge over many times to copy all the files.</li>
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</ul>
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<p> Copy performance is always better when both the source and target
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volumes are in the same library and when setting the COPYTYPE parameter for
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that library controller to *IOP. Two conditions exist that require an extra
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processing step. The first one is that the source and target volumes are in
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different libraries. The second involves setting the COPYTYPE parameter to
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*SYSTEM and having the volumes exist in the same library. This extra step
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requires moving the files you want to copy to temporary storage on the iSeries™ server
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before writing them to the target volume. You do not need to use temporary
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storage when the system meets both of the following conditions:</p>
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<ul><li>Both optical volumes are in the same library.</li>
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<li>You set the COPYTYPE parameter on the CPYOPT command to *IOP.</li>
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</ul>
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<p>These two conditions allows for the direct transfer of data between
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the two optical drives.</p>
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</div>
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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="rzam4cpyopt.htm" title="This topic discusses the Copy Optical (CPYOPT) CL command and some of the optional parameters which you can specify.">Copy optical (CPYOPT)</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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