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FlexCache slow read performance and cache eviction

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Applies to

  • ONTAP 9.12.1
  • NFSv3
  • FlexCache

Issue

  • FlexCache volumes exhibit slow read performance during trading process startup.
  • Files previously read in full via FlexCache are not consistently present in cache, resulting in slow re-reads.
  • No evidence of cache volume nearing 90% utilization; volume usage is reported at 4%.
  • Origin files are not updated after creation; atime updates are disabled on both origin and FlexCache volumes.
  • Cache is mounted read-only on all clients.
  • Unable to pre-populate cache contents due to dynamic trading strategies and limited available capacity.
  • Customer seeks a method to programmatically list cache contents and validate which files are fully or partially cached.
  • Documentation (TR-4743) does not provide sufficient detail on cache expiration or eviction conditions.
  • Business impact is confirmed: slow reads affect startup operations across multiple remote facilities.
  • Scrubbed Example CLI output:
    Clus_1::> vol show FC_algolive_blob
    Vserver Volume Aggregate State Type Size Available Used%
    svm_toast_599 FC_algolive_blob - online RW 2.99TB 2.84TB 4%
    2nd_Clus::> vol show -vserver SVM_toast_2000 -volume algolive_blob -fields atime-update
    vserver volume atime-update
    SVM_toast_2000 algolive_blob false
    Clus_1::    > vol show -vserver svm_toast_599 -volume FC_algolive_blob -fields atime-update
    vserver volume atime-update
    svm_toast_599 FC_algolive_blob false
  • Issue first observed: 2025-10-06.
  • No recent changes except origin cluster upgrade to ONTAP 9.16.1P6 about 26 days prior.
  • Multiple files affected; example paths provided.

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