http://wiki.opensfs.org/index.php?title=DNE_StripedDirectories_HighLevelDesign_wiki_version&feed=atom&action=historyDNE StripedDirectories HighLevelDesign wiki version - Revision history2024-03-28T10:03:25ZRevision history for this page on the wikiMediaWiki 1.39.3http://wiki.opensfs.org/index.php?title=DNE_StripedDirectories_HighLevelDesign_wiki_version&diff=1952&oldid=prevRichardHenwood: /* Functional Statement */2015-07-17T17:44:12Z<p><span dir="auto"><span class="autocomment">Functional Statement</span></span></p>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Similar to file striping, a striped directory will split the name entries across multiple MDTs. Each MDT keeps directory entries for certain range of hash space. For example, there are N MDTs and hash range is 0 to <code>MAX_HASH</code>, first MDT will keep records with hashes <code>[0, MAX_HASH/N - 1]</code>, second one with hashes <code>[MAX_HASH / N, 2 * MAX_HASH / N]</code> and so on. During file creation, LMV will calculate the hash value by the name, then create the file in the corresponding stripe on one MDT. It will also allow the user to choose different hash function to stripe the directory. The directory can only be striped during creation and can not be re-striped after creation in DNE phase II.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Similar to file striping, a striped directory will split the name entries across multiple MDTs. Each MDT keeps directory entries for certain range of hash space. For example, there are N MDTs and hash range is 0 to <code>MAX_HASH</code>, first MDT will keep records with hashes <code>[0, MAX_HASH/N - 1]</code>, second one with hashes <code>[MAX_HASH / N, 2 * MAX_HASH / N]</code> and so on. During file creation, LMV will calculate the hash value by the name, then create the file in the corresponding stripe on one MDT. It will also allow the user to choose different hash function to stripe the directory. The directory can only be striped during creation and can not be re-striped after creation in DNE phase II.</div></td></tr>
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<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>[[Image:<del style="font-weight: bold; text-decoration: none;">hld_files/stripe_hash.png|Di Wang > DNE Phase II Striped Directory High Level Design > </del>stripe_hash.png]]</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>[[Image:stripe_hash.png]]</div></td></tr>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[AED: this diagram is not correct. Stripe 0 does not hold [0, max_hash/4] and stripe 1 does not hold [max_hash/4, max_hash/2], etc. Instead, it would be better to show stripe 0 holding [hash % 4 == 0], and stripe 1 holding [hash % 4 == 1]. ]</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[AED: this diagram is not correct. Stripe 0 does not hold [0, max_hash/4] and stripe 1 does not hold [max_hash/4, max_hash/2], etc. Instead, it would be better to show stripe 0 holding [hash % 4 == 0], and stripe 1 holding [hash % 4 == 1]. ]</div></td></tr>
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</table>RichardHenwoodhttp://wiki.opensfs.org/index.php?title=DNE_StripedDirectories_HighLevelDesign_wiki_version&diff=1950&oldid=prevRichardHenwood: /* Update buffer for creating striped directory */2015-07-17T17:43:21Z<p><span dir="auto"><span class="autocomment">Update buffer for creating striped directory</span></span></p>
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</table>RichardHenwoodhttp://wiki.opensfs.org/index.php?title=DNE_StripedDirectories_HighLevelDesign_wiki_version&diff=1948&oldid=prevRichardHenwood: /* Implementation */2015-07-17T17:41:31Z<p><span dir="auto"><span class="autocomment">Implementation</span></span></p>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Note: LDLM lock is not needed during recovery.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Note: LDLM lock is not needed during recovery.</div></td></tr>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>This design ensures the all directories will be migrated to the new MDT in all cases.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>This design ensures the all directories will be migrated to the new MDT in all cases.</div></td></tr>
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<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>After migrating the directory to the new MDT the directory on the old MDT will become an orphan, i.e. it can not be accessed from the namespace. The orphan can not be destroyed until all of its children are moved to the new MDT. In this way, migrating a directory does not need to update the parent FID in the linkEA of all of the children since all of children can still find its parent on the old MDT using fid2path during migration. </div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>After migrating the directory to the new MDT the directory on the old MDT will become an orphan, i.e. it can not be accessed from the namespace. The orphan can not be destroyed until all of its children are moved to the new MDT. In this way, migrating a directory does not need to update the parent FID in the linkEA of all of the children since all of children can still find its parent on the old MDT using fid2path during migration.</div></td></tr>
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</table>RichardHenwoodhttp://wiki.opensfs.org/index.php?title=DNE_StripedDirectories_HighLevelDesign_wiki_version&diff=1946&oldid=prevRichardHenwood: Created page with " = Introduction = With the release of DNE Phase I Remote Directories, Lustre* file systems now support more than one MDT in a single filesystem. This feature has some limit..."2015-07-17T17:38:03Z<p>Created page with " = Introduction = With the release of DNE Phase I Remote Directories, Lustre* file systems now support more than one MDT in a single filesystem. This feature has some limit..."</p>
<a href="http://wiki.opensfs.org/index.php?title=DNE_StripedDirectories_HighLevelDesign_wiki_version&diff=1946">Show changes</a>RichardHenwood