Creating a QoS Policy

A QoS policy is a group of I/O performance targets. This operation enables you to dynamically allocate storage resources to meet a specified performance objective of a certain application.

Precautions

The user host aggregates I/Os for specific service models. As a result, the IOPS of services received by the storage system is lower than that delivered by the host application. If the IOPS upper limit in a QoS policy is set based on the IOPS of services delivered by the host application, the QoS policy cannot limit the IOPS of services on the storage system effectively. In this case, you can lower the IOPS upper limit or configure a bandwidth upper limit in the QoS policy.

Procedure

  1. Choose Services > Block Service > QoS Policy.
  2. Click Create.

    The Create QoS Policy page is displayed.

  3. Set a QoS policy name.

    • A name must be unique.
    • A name can only contain digits, letters, underscores (_), and hyphens (-) and must start with a digit or letter.
    • The name contains 1 to 63 characters.

  4. Set basic parameters of the QoS policy in either of the following ways, including By performance density and upper limits and By read and write upper limits.

    • By performance density and upper limits

      Table 1 describes related parameters.

      Table 1 QoS policy parameters

      Parameter

      Description

      IOPS/GB

      Indicates the maximum number of read/write operations that can be performed on an object per second per GB.

      Max. IOPS

      Indicates the maximum number of read/write operations that can be performed on an object per second.

      NOTE:
      Calculate the effective maximum IOPS in the QoS policy as follows:
      1. Calculate (IOPS/GB x Object capacity) + 100.
      2. Compare the calculation result obtained in 1 with Max. IOPS. The smaller of the two values is the effective maximum IOPS.

      Suppose that IOPS/GB is 2, object capacity is 100 GB, and Max. IOPS is 1000. The effective maximum IOPS in the QoS policy is 300 (that is, 2 x 100 + 100), because 300 is smaller than 1000.

      Burst IOPS/Duration

      Indicates the maximum number of read/write operations that can be performed on an object per second within a specified period when the burst function is enabled.

      • Burst IOPS: indicates the maximum number of read/write operations that can be performed on an object per second when the burst function is enabled.
        NOTE:
        • The burst function boosts the IOPS of an object within a specified period of time, temporarily improving object performance.
        • The system compares the effective maximum IOPS for an object with the burst IOPS. If the effective maximum IOPS is smaller, the burst function is enabled.
      • Burst duration: indicates the minimum period during which the burst function is enabled for an object.

      MBPS/TB

      Indicates the maximum amount of data that can be transmitted on an object per second per TB.

      Max. MBPS

      Indicates the maximum amount of data that can be transmitted on an object per second.

      NOTE:
      Calculate the effective maximum MBPS in the QoS policy as follows:
      1. Calculate (MBPS/TB x Object capacity) + 5.
      2. Compare the calculation result obtained in 1 with Max. MBPS. The smaller of the two values is the effective maximum MBPS.

      Suppose that MBPS/TB is 20, object capacity is 2 TB, and Max. MBPS is 100. The effective maximum MBPS in the QoS policy is 45 (that is, 20 x 2 + 5), because 45 is smaller than 100.

      Burst MBPS/TB
      Indicates the maximum amount of data that can be transmitted on an object per second per TB when the burst function is enabled.
      NOTE:
      • The burst function boosts the amount of data that can be transmitted per second, temporarily improving object performance.
      • Maximum bandwidth of a single object when the burst function is enabled = Burst MBPS/TB x Volume capacity
      • The system compares the maximum MBPS that actually takes effect for an object with the value of (Burst MBPS/TB x Volume capacity). If the maximum MBPS is smaller, the burst function is enabled for the object.
    • By read and write upper limits

      Table 2 describes related parameters.

      Table 2 QoS policy parameters

      Parameter

      Description

      Max. Read IOPS

      Indicates the maximum number of read operations that can be performed per second.

      Max. Write IOPS

      Indicates the maximum number of write operations that can be performed per second.

      Max. Read MBPS

      Indicates the maximum amount of data that can be read per second.

      Max. Write MBPS

      Indicates the maximum amount of data that can be written per second.

  5. Set a trigger policy for the QoS policy. Possible options are One-off, Daily, Weekly, and Always.

    • One-off: The QoS policy takes effect once at the specified time.
      1. In Start Date, set the date when the policy takes effect.
      2. In Start Time, set the time when the policy takes effect.
      3. In Duration, set the duration over which the policy remains in effect.

        The duration ranges from 30 minutes to 24 hours.

    • Daily: The QoS policy takes effect daily.
      1. In Start Date, set the date when the policy takes effect.
      2. In Start Time, set the time when the policy takes effect every day.
      3. In Duration, set the duration over which the policy remains in effect.

        The duration ranges from 30 minutes to 24 hours.

    • Weekly: The QoS policy takes effect weekly.
      1. In Start Date, set the date when the policy takes effect and the day when the policy takes effect every week.
      2. In Start Time, set the time when the policy takes effect every specified day of the week.
      3. In Duration, set the duration over which the policy remains in effect.

        The duration ranges from 30 minutes to 24 hours.

    • Always: The QoS policy remains in effect all the time.

  6. Click OK.
  7. Confirm your operation as prompted.
Parent topic: Configuring the Block Service