Why is there a difference between statistics volume and AIQUM iop counts?

Applies to

ONTAP 9

OnCommand Unified Manager (OCUM)

ActiveIQ Unified Manager (AIQUM)

Answer

• The volume layer, or WAFL layer, is a maximum of 64kB in size.
• The protocol (LUN or CIFS/NFS operations) can be bigger (65kB to megabytes in size) in operation size.
• Multiple operations are broken up into parallel 64kB requests between the protocol and WAFL.
• This may also impact a QoS policy:
  • QoS policies engage at protocol layer operation counts.

Example: Microsoft SQL may do database queries on a LUN in 256kB sequential reads which translate to 4 64kB WAFL read messages.

Additional Information

• To compare the two, you can use the following commands:
  • Cluster::> set diag -c off; statistics start -object volume-vserver <SVM name> -instance <volume name> -node <node where data LIF is>
  • Cluster::> qos statistics volume performance show -vserver <SVM name> -volume <volume name>
• NetApp Harvest volume view shows metrics from the WAFL layer (similar to statistics start -object volume).

Example: Screenshots of IOPs from Harvest and AIQUM