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How do you identify the source of reads for a workload in ONTAP 9?

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Applies to

  • ONTAP 9
  • Cloud Volume ONTAP 9

Answer

  • The workload_volume CM object has a counter called read_io_type which can be used to identify the sources of reads.
  • Use the commands to get the output:
    • Cluster::> set -privilege diagnostic
    • Cluster::*> statistics start -object workload_volume -counter read_io_type
    • Cluster::*> statistics show
    • Cluster::*> statistics stop
  • The following are all the different read sources:
Counter Description
read_io_type.cache Reads from system RAM
read_io_type.pmem Read from persistent memory
read_io_type.ext_cache Reads from Flash Cache
read_io_type.disk Reads from an HDD aggregate
read_io_type.bamboo_ssd Reads from an SSD aggregate
read_io_type.hya_hdd Reads from Flash Pool HDD RAID group
read_io_type.hya_cache Reads from Flash Pool SSD RAID group
read_io_type.hya_non_cache Not used
read_io_type.cloud Reads from composite aggregate (FabricPool cold tier)
read_io_type.fc_miss Reads from FlexCache origin and remote retrieves like a remote FG member (missed cache lookup)
read_io_type.cloud_s2c Non FabricPool cloud reads such as restores from SnapMirror to Cloud solution

 

Additional Information

How to check if FlashPool or FlashCache is effectively caching reads

 

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