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Version: 3.1

Application I/O control in Tanzu

Portworx volumes are created from a common storage pool and share their available IOPS and bandwidth between all other provisioned Portworx volumes. If an application's volumes start consuming too many resources, it can become a "noisy neighbor" and reduce the I/O and network bandwidth available to other volumes in the pool.

The Portworx Application I/O Control feature provides you with a method for controlling an individual Portworx volume’s IOPS or bandwidth usage from within your cluster. You can define quotas through a StorageClass which prevent any applications from using excessive bandwidth. When you need to adjust the bandwidth, you can do so in real-time by updating the values in the StorageClass. The updated configuration will be applied to new volumes created after the change.

In addition to defining parameters in a StorageClass, you can set Application I/O Control values for volumes using the pxctl command line interface.

note

By default, this feature is not enabled.

Prerequisites​

  • Application I/O Control is supported for kernel 4.6 or higher.
  • Only the cgroup mount path /sys/fs/cgroup/blkio is supported. This is typically set by mount -t cgroup -o blkio none /sys/fs/cgroup/blkio. Uncommon distributions could have a different cgroup mount path.

Create volumes​

note

  • You can set a maximum rate for IOPS and a maximum rate for bandwidth at the same time. However, you cannot set a read parameter for both IOPS and bandwidth at the same time or a write parameter for both at the same time. For example, setting --max_iops 1024,off --max_bandwidth off,2 will work, but setting --max_iops 1024,off --max_bandwidth 2,off will prompt error.

  • Once you set Application I/O Control values, you can check alerts or logs for messages indicating that Application I/O Control is not enabled. For example: IO throttling supported from kernel v4.6, this node has kernel v3.10 indicates that Application I/O Control is not supported.

  • IOPS might be misleading due to batching of small blocksize IOs into a larger one before IO reaches the pxd device, especially when using sharedV4 volumes. Bandwidth throttling is more consistent.

Apply using a StorageClass​

You can apply Application I/O Control through a StorageClass.

To configure IOPS throttling in a StorageClass, use the following format:

kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
  name: portworx-io-profile
provisioner: pxd.portworx.com
parameters:
  repl: "2"
  io_profile: "db_remote"
  io_throttle_rd_iops: "1024"
  io_throttle_wr_iops: "1024"

To configure bandwidth throttling in a StorageClass, use the following format:

kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
  name: portworx-io-profile
provisioner: pxd.portworx.com
parameters:
  repl: "2"
  io_profile: "db_remote"
  io_throttle_rd_bw: "10"
  io_throttle_wr_bw: "10"

You can also configure read IOPS throttling and write bandwidth throttling, or the inverse. For example:

kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
  name: portworx-io-profile
provisioner: pxd.portworx.com
parameters:
  repl: "2"
  io_profile: "db_remote"
  io_throttle_rd_iops: "1024"
  io_throttle_wr_bw: "10"
note

The minimum value for rd_bw and wr_bw is 1, and the minimum value for rd_iops and wr_iops is 256.

Create using pxctl​

When you create volumes using pxctl, you can specify the --max_bandwidth and --max_iops flags to restrict the storage resources that volume uses:

pxctl volume create --max_bandwidth <ReadBW>,<WriteBW> <volname/volid> 
pxctl volume create --max_iops <ReadIOPS>,<WriteIOPS> <volname/volid>
note

The minimum value for --max_bandwidth is 1, and the minimum value for --max_iops is 256.

Update volumes using pxctl​

If you want to add Application I/O Control to an existing volume, or change its throttling values, you can do so using the --max_bandwidth and --max_iops flags with the pxctl volume update commands:

pxctl volume update --max_bandwidth <ReadBW>,<WriteBW> <volname/volid> 
pxctl volume update --max_iops <ReadIOPS>,<WriteIOPS> <volname/volid>
note

If you want to limit only read or write bandwidth/IOPS traffic, set the other value to off.

For example: Set read throttling for an existing volume to 1024 IOPS:

pxctl volume update --max_iops 1024,off exampleVolume

Remove throttling​

If you want to remove throttling from a volume, set the value of the --max_bandwidth and --max_iops flags to off for any throttling you wish to remove:

pxctl volume update --max_bandwidth off,<WriteBW> <volname/volid>
pxctl volume update --max_iops off,off <volname/volid>
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