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CONTAP-45637: Read latency because of high IO queued on HDDs

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Issue

  • Similar to bug 1444991, high queued i/o is seen on a specific drive or set of drives.
  • Example:
    [cluster1::*> statistics start -object disk -counter disk_busy|io_pending|io_queued|total_transfers -sample-id disk_queued

Statistics collection is being started for sample-id: disk_queued]
  • Example:
  • The Disk:4.1.18 & 4.1.30 , both are serving almost equal no. of IOPS, however the IOs queued on Disk 4.1.18 is high and the Disk is 100% busy.
  • Look for one or few such disks in the system.

[cluster1::*> statistics show -sample-id disk_queued

Object: disk
Instance: 4.1.18
Start-time: 2/13/2023 10:05:11
End-time: 2/13/2023 10:05:17
Elapsed-time: 6s
Scope: cluster1-01
Number of Constituents: 1 (complete_aggregation)
Counter Value
-------------------------------- --------------------------------
disk_busy 100% <--
io_pending 7.99
io_queued 600.08 <--
total_transfers 378

 

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