very high IO utilization after upgrade from mongo 3.6 to 4.0.18

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    • Type: Bug
    • Resolution: Duplicate
    • Priority: Major - P3
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    • Affects Version/s: 4.0.18
    • Component/s: None
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    • 3
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      We upgraded our sharded cluster from mongo 3.6 to 4.0.18 on Linux Stretch. Since then IO utilization is almost always at 100%Unable to render embedded object: File ( Almost all monitored metrics look worse than before the upgrade) not found. I'll attach a screenshot where you can see that IO utilization went up to almost constant 100% at around 0:00 o'clock when we upgraded the shard to mongodb 4.0.18 

      We did not yet set FCV to 4.0 to allow our deployment to run without enabling these features for a burn-in period to ensure the likelihood of downgrade is minimal - as suggested in mongodb's documentation.

      Any help is greatly appreciated because this issue becomes critical!

        1. Bildschirmfoto 2020-06-10 um 11.10.04.png
          Bildschirmfoto 2020-06-10 um 11.10.04.png
          282 kB
        2. disk_reads.png
          disk_reads.png
          152 kB
        3. PrimaryAfterDowngrade.png
          PrimaryAfterDowngrade.png
          713 kB
        4. PrimaryAfterUpgrade.png
          PrimaryAfterUpgrade.png
          1.02 MB

            Assignee:
            Dmitry Agranat
            Reporter:
            Kay Agahd
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              Created:
              Updated:
              Resolved: