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<b>Transition of the Farm /cache filesystem to read-only from farm and ifarm</b> </div>
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<b>What is changing?</b> </div>
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On November 19, 2024, during monthly maintenance, the /cache filesystem will be changed to read-only access from farm, ifarm, Globus, and XRootD Data Transfer Nodes. After that date, files will only be copied to /cache via in the following ways: </div>
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The jcache command, which reads files from tape and writes them into /cache </div>
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The jput command, which writes files to tape and can optionally place a copy immediately in /cache when the<i> -cache</i> flag is specified </div>
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Data ingest from the experimental halls using the jmirror command with a regular expression pattern match for data retention in cache. </div>
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<b>Why is this happening?</b> </div>
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The new system will ensure that files move to tape promptly and that /cache is an accurate subset of files stored on tape. </div>
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In the current /cache filesystem, there are a commonly cases where files are in conflict with tape storage, leading to work slow downs. </div>
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Small file handling has been a historic problem, and many small files in /cache were not stored on tape or backed up in any way </div>
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<b>How will this affect farm job workflows?</b> </div>
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Jobs that are part of a SWIF workflow with an output specification to /cache will continue to work. </div>
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Jobs that attempt to write directly to cache using open(), cp, mv, or other POSIX tools will fail. Output from slurm jobs that are not part a SWIF workflow should be stored on /volatile and will need to be moved to tape manually using jput on ifarm. Generally,
slurm workflows that need to interact with tape would be better implemented using SWIF. </div>
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Note that jput is not available on (non-interactive) farm nodes because it may queue, stalling the farm node and potentially timing out the job. </div>
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<b>What is not changing?</b> </div>
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Cache deletion policy: remains unchanged. </div>
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Cache file pinning: continues to work as before. </div>
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jcache client: continues to work as before.</div>
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SWIF outputs to /cache: continues to work as before.</li></ul>
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References: </div>
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KBA: <u><a href="https://jlab.servicenowservices.com/scicomp?id=kb_article_view&sysparm_article=KB0015468" id="LPlnk243594" class="OWAAutoLink" title="https://jlab.servicenowservices.com/scicomp?id=kb_article_view&sysparm_article=KB0015468">Migration to read-only
cache</a></u> </div>
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KBA: <span style="color: rgb(5, 99, 193);"><u><a href="https://jlab.servicenowservices.com/scicomp?id=kb_article_view&sysparm_article=KB0014686" target="_blank" id="OWA1a162a9c-73af-e73f-bfbe-cb70093cac25" class="Hyperlink SCXW7131722 BCX0 OWAAutoLink" rel="noreferrer noopener" style="color: rgb(5, 99, 193); margin: 0px;">Computing
Coordinators</a></u></span> </div>
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