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Set a throughput ceiling with QoS in ONTAP

Contributors netapp-aaron-holt netapp-thomi netapp-aherbin
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You can use the max-throughput field for a policy group to define a throughput ceiling for storage object workloads (QoS Max). You can apply the policy group when you create or modify the storage object.

What you'll need

  • You must be a cluster administrator to create a policy group.

  • You must be a cluster administrator to apply a policy group to an SVM.

About this task

  • Beginning with ONTAP 9.4, you can use a non-shared QoS policy group to specify that the defined throughput ceiling applies to each member workload individually. Otherwise, the policy group is shared: the total throughput for the workloads assigned to the policy group cannot exceed the specified ceiling.

    Set -is-shared=false for the qos policy-group create command to specify a non-shared policygroup.

  • You can specify the throughput limit for the ceiling in IOPS, MB/s, or IOPS, MB/s. If you specify both IOPS and MB/s, whichever limit is reached first is enforced.

    Note

    If you set a ceiling and a floor for the same workload, you can specify the throughput limit for the ceiling in IOPS only.

  • A storage object that is subject to a QoS limit must be contained by the SVM to which the policy group belongs. Multiple policy groups can belong to the same SVM.

  • You cannot assign a storage object to a policy group if its containing object or its child objects belong to the policy group.

  • It is a QoS best practice to apply a policy group to the same type of storage objects.

Steps

  1. Create a policy group:

    qos policy-group create -policy-group policy_group -vserver SVM -max-throughput number_of_iops|Mb/S|iops,Mb/S -is-shared true|false

    Learn more about qos policy-group create in the ONTAP command reference. You can use the qos policy-group modify command to adjust throughput ceilings.

    The following command creates the shared policy group pg-vs1 with a maximum throughput of 5,000 IOPS:

    cluster1::> qos policy-group create -policy-group pg-vs1 -vserver vs1 -max-throughput 5000iops -is-shared true

    The following command creates the non-shared policy group pg-vs3 with a maximum throughput of 100 IOPS and 400 Kb/S:

    cluster1::> qos policy-group create -policy-group pg-vs3 -vserver vs3 -max-throughput 100iops,400KB/s -is-shared false

    The following command creates the non-shared policy group pg-vs4 without a throughput limit:

    cluster1::> qos policy-group create -policy-group pg-vs4 -vserver vs4 -is-shared false

  2. Apply a policy group to an SVM, file, volume, or LUN:

    storage_object create -vserver SVM -qos-policy-group policy_group

    Learn more about the commands described in this procedure in the ONTAP command reference. You can use the storage_object modify command to apply a different policy group to the storage object.

    The following command applies policy group pg-vs1 to SVM vs1:

    cluster1::> vserver create -vserver vs1 -qos-policy-group pg-vs1

    The following commands apply policy group pg-app to the volumes app1 and app2:

    cluster1::> volume create -vserver vs2 -volume app1 -aggregate aggr1 -qos-policy-group pg-app
    cluster1::> volume create -vserver vs2 -volume app2 -aggregate aggr1 -qos-policy-group pg-app

  3. Monitor policy group performance:

    qos statistics performance show

    Learn more about qos statistics performance show in the ONTAP command reference.

    Note

    Monitor performance from the cluster. Do not use a tool on the host to monitor performance.

    The following command shows policy group performance:

    cluster1::> qos statistics performance show
Policy Group           IOPS      Throughput   Latency
-------------------- -------- --------------- ----------
-total-                 12316       47.76MB/s  1264.00us
pg_vs1                   5008       19.56MB/s     2.45ms
_System-Best-Effort        62       13.36KB/s     4.13ms
_System-Background         30           0KB/s        0ms

  4. Monitor workload performance:

    qos statistics workload performance show

    Learn more about qos statistics workload performance show in the ONTAP command reference.

    Note

    Monitor performance from the cluster. Do not use a tool on the host to monitor performance.

    The following command shows workload performance:

    cluster1::> qos statistics workload performance show
Workload          ID     IOPS      Throughput    Latency
--------------- ------ -------- ---------------- ----------
-total-              -    12320        47.84MB/s  1215.00us
app1-wid7967      7967     7219        28.20MB/s   319.00us
vs1-wid12279     12279     5026        19.63MB/s     2.52ms
_USERSPACE_APPS     14       55        10.92KB/s   236.00us
_Scan_Backgro..   5688       20            0KB/s        0ms
    Note

    You can use the qos statistics workload latency show command to view detailed latency statistics for QoS workloads. Learn more about qos statistics workload latency show in the ONTAP command reference.