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What are the statistics used to measure indirect data access to LUNs in ONTAP 9?

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Applies to

ONTAP 9

Answer

What is Indirect Data Access to a LUN?

This is access to a LUN through a LIF configured on a node other than the node that ‘owns’ the aggregate on which the LUN data is stored. This can occur due to one or more of the following scenarios:

  • When host multipathing software is not configured properly and uses a non-optimized path for data transfer
  • When the node owning a LUN does not have a SAN LIF configured
  • When the LUNs Selective LUN Map configuration does not allow direct access
  • When portsets are misconfigured and preventing direct access
  • When errors on the fabric cause the host to retry I/O against non-optimized paths

Note: Remote ops may be recording following any change to the owning node for a LUN, such as storage failover events (takeover/giveback) or LUN move operations. A small number of ops may be normal in some configurations, due to path checking performed by the initiator.

The following are the two counters that should be considered to measure indirect data access to LUNs in clustered Data ONTAP:

  • remote_ops
  • remote_bytes

::> set advanced

::*> statistics show-periodic -object lun -vserver <vserver_name> -instance <lun_path> -counter remote_ops|remote_bytes

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