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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:Calibri">The ChangeLogs do have limits on the number of records, but hitting that limit will _also_ result in ENOSPC, as would also happen if the MDT actually runs out of space. Alex has a patch
in flight that reduces the maximum llog size if the MDT is running out of space, so that the old logs can be closed and cleaned up rather than continuing to grow even though they are mostly empty. There was also a patch landed from Artem to add a /proc file
that reports the current ChangeLog size to userspace so that this can be tracked. <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:Calibri"><br>
We did discuss what should happen if the ChangeLog is running out of space for new records (e.g. because some consumer is not consuming). It should be tunable by the admin, either to drop the consumer and delete all of the records for that consumer, or to
prevent new operations being performed in the filesystem (e.g. if it was critical to not lose any records for some reason). I'd suspect the first option would be the better default.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:Calibri"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:Calibri">No idea about the other items. Hopefully someone else can reply.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:Calibri"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:Calibri;color:black">Cheers, Andreas<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:Calibri;color:black">-- <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:Calibri;color:black">Andreas Dilger<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:Calibri;color:black">Lustre Principal Architect<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:Calibri;color:black">Intel High Performance Data Division</span><span style="font-size:11.0pt;font-family:Calibri"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:Calibri"><o:p> </o:p></span></p>
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<p class="MsoNormal">On 2016/06/23, 18:10, "Nathan Rutman" <<a href="mailto:nathan.rutman@seagate.com">nathan.rutman@seagate.com</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Hi all - <o:p></o:p></p>
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<p class="MsoNormal">I have a number of nagging concerns about current HSM implementation; maybe I'm just out of date, but I figure this is the place to ask:<o:p></o:p></p>
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<p class="MsoNormal">1. Changelog size limits. Can changelogs still grow unbounded, resulting in ENOSPC (or worse) on the MDS? Should there be a size limit? What should be done at that limit -- stop recording changelogs? Turn FS read-only?<o:p></o:p></p>
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<p class="MsoNormal">2. Coordinator queue limit. Can coordinator queue grow unbounded? Can we add some throttling from the coordinator to the PE, maybe an -EAGAIN if the coordinator queue is large?<o:p></o:p></p>
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<p class="MsoNormal">3. Error-condition passthrough from hsmtool back to PE. Backend may have e.g. ENOSPC, reported back to coordinator, but then what? Can future PE requests be denied by the coordinator with an ENOSPC, presumably prompting Robinhood to issue
hsm_remove commands? ENOSPC should continue to be returned, until some other rv is returned by copytool.<o:p></o:p></p>
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<p class="MsoNormal">4. Coordinator should sort incoming requests so that "restores" and "removes" are placed before "archives". Restores are the highest priority from user point of view, and removes are next from a space available point of view.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><b>--</b> <o:p></o:p></p>
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<p class="MsoNormal"><b><span style="font-size:7.5pt">Nathan Rutman · <span style="color:#666666">Principal Systems Architect</span><br>
<span style="color:#0B5394">Seagate Technology</span> · </span></b><span style="font-size:7.5pt">+1 503 877-9507<b> ·
</b>GMT-8</span><o:p></o:p></p>
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