https://jira.whamcloud.com This file is an XML representation of an issue en-us 9.4.14 940014 05-12-2023 https://jira.whamcloud.com/browse/LU-14512 Lustre <p>Otherwise a FLR file could be created which contains multiple updated mirrors but their contents do not match.</p> LU-14512

prohibit extend file with stale mirror

Bug Minor Closed Not a Bug Zhenyu Xu Zhenyu Xu Thu, 11 Mar 2021 15:38:36 +0000 Sat, 13 Mar 2021 14:54:25 +0000 Sat, 13 Mar 2021 14:54:25 +0000 0 5 <p>how this can be? my understanding is that extending itself can't introduce any inconsistency as it copies data from replica known to be correct?</p> <p>Bobi Jam (bobijam@hotmail.com) uploaded a new patch: <a href="https://review.whamcloud.com/42008" class="external-link" target="_blank" rel="nofollow noopener">https://review.whamcloud.com/42008</a><br/> Subject: <a href="https://jira.whamcloud.com/browse/LU-14512" title="prohibit extend file with stale mirror" class="issue-link" data-issue-key="LU-14512"><del>LU-14512</del></a> flr: prohibit extend file with stale mirror<br/> Project: fs/lustre-release<br/> Branch: master<br/> Current Patch Set: 1<br/> Commit: a5b1e28b5e5607863cd91da6c6155d99c8f4c988</p> <p>IIRC, mirror extend does not do the resync, only merge the layout and bring its data, or extend to create a new mirror with empty data.</p> <blockquote> <p>IIRC, mirror extend does not do the resync, only merge the layout and bring its data, or extend to create a new mirror with empty data.</p></blockquote> <p>well, no, lfs mirror extend -N creates a mirror and (re)sync it</p> <p>you are right. </p> <p>There's another issue, as the file contains updated mirror1 and stale mirror2 (in write-pending state), it extends a mirror3 with data migrated from mirror1, lod_declare_update_write_pending() would fail the assertion that a FLR in write shouldn't contain multiple primary mirrors.</p> <p>probably <a href="https://review.whamcloud.com/#/c/42003/4" class="external-link" target="_blank" rel="nofollow noopener">https://review.whamcloud.com/#/c/42003/4</a> can help with that?</p> <p>yes that can help. Is it a good idea to prohibit un-synced FLR file to extend new mirror in general? </p> <p>I'm not sure. probably someone else can comment on this rather practical question?</p> <blockquote> <p>Is it a good idea to prohibit un-synced FLR file to extend new mirror in general? </p></blockquote> <p>No, I don't think that is a good idea to impose that limitation.</p> <p>Consider a file with mirror1 (primary), mirror2 (stale). If mirror2 is on a failed OST, we may want to create a whole new mirror3 to restore redundancy, and then delete mirror2. It should always be possible to create a new mirror as long as there is a non-stale mirror.</p> <p>In the FLR case, the stale mirror may be an older version of the file (<a href="https://jira.whamcloud.com/browse/LU-12648" title="FLR2: File versioning with FLR and &quot;nosync&quot; files" class="issue-link" data-issue-key="LU-12648">LU-12648</a>) that is still useful, or may still have good data at the start of a file (common case of appending write) that could be manually recovered.</p> <p>Note that it is better to add the new mirror to the file <b>before</b> removing the stale mirror, in case there are also some non-overlapping errors in the remaining (non-stale) mirror. This often happens in RAID arrays that a drive partly fails, and then during resync there are also sector errors on the "good" drive, and if the bad drive is still partly available the few bad sectors can still be recovered.</p> Related LU-14514 LU-13730 LU-13720 Development Rank 1|i01p5r: Rank (Obsolete) 9223372036854775807 Severity