VMware IO stress

VMware IO stress causes disk stress on the target VMware VMs. It aims to verify the resilience of applications that share this disk resource with the VM.

Usage

View the uses of the fault

This fault helps determine how resilient an application is to unexpected spikes in resources. It determines how well an application handles unexpected stress at a given point in time. It simulates slower disk operations by the application and nosiy neighbour problems by hogging the disk bandwidth. It also verifies the disk performance on increasing I/O threads and varying I/O block sizes. It checks if the application functions under high disk latency conditions, when I/O traffic is very high and includes large I/O blocks, and when other services monopolize the I/O disks.

Prerequisites

• Kubernetes > 1.16
• Execution plane is connected to vCenter and the hosts on port 443.
• VMware tool is installed on the target VM with remote execution enabled.
• Adequate vCenter permissions to access the hosts and the VMs.
• Create a Kubernetes secret that has the Vcenter credentials in the CHAOS_NAMESPACE. Below is a sample secret file:

apiVersion: v1
kind: Secret
metadata:
  name: vcenter-secret
  namespace: litmus
type: Opaque
stringData:
    VCENTERSERVER: XXXXXXXXXXX
    VCENTERUSER: XXXXXXXXXXXXX
    VCENTERPASS: XXXXXXXXXXXXX

Note

You can pass the VM credentials as secrets or as a ChaosEngine environment variable.

Default validations

The VM should be in a healthy state.

Fault tunables

Fault tunables

Mandatory fields

Variables	Description	Notes
VM_NAME	Name of the target VM.	For example, ubuntu-vm-1.

Optional fields

Variables	Description	Notes
FILESYSTEM_UTILIZATION_PERCENTAGE	Specify the size as a percentage of free space on the file system.	For example, 40.
FILESYSTEM_UTILIZATION_BYTES	Specify the size in gigabytes(GB). FILESYSTEM_UTILIZATION_PERCENTAGE and FILESYSTEM_UTILIZATION_BYTES environment variables are mutually exclusive. If both are provided, FILESYSTEM_UTILIZATION_PERCENTAGE takes precedence.	For example, 100
NUMBER_OF_WORKERS	Number of I/O workers involved in I/O disk stress.	Defaults to 4
VOLUME_MOUNT_PATH	Location that points to the volume mount path used in I/O stress.	For example, /Users/admin/disk-02.
CPU_CORES	Number of CPU cores that are subject to CPU stress.	Defaults to 1.
TOTAL_CHAOS_DURATION	Duration that you specify, through which chaos is injected into the target resource (in seconds).	Defaults to 30s.
CHAOS_INTERVAL	Time interval between two successive instance terminations (in seconds).	Defaults to 30s.
SEQUENCE	Sequence of chaos execution for multiple instances.	Defaults to parallel. Supports serial sequence as well.
RAMP_TIME	Period to wait before and after injecting chaos (in seconds).	For example, 30s.

Fault examples

Common fault tunables

Refer to the common attributes to tune the common tunables for all the faults.

Filesystem utilization percentage

It specifes the size as a percentage of free space on the file system. You can tune it using the FILESYSTEM_UTILIZATION_PERCENTAGE environment variable.

Use the following example to tune it:

# io-stress in the VMware VM
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: VMware-io-stress
    spec:
      components:
        env:
        # Name of the VM
        - name: VM_NAME
          value: 'test-vm-01'
        # percentage of free space of file system, need to be stressed
        - name: FILESYSTEM_UTILIZATION_PERCENTAGE
          value: '10'

Filesystem utilization bytes

It specifies the amount of free space on the file system in gigabytes(GB). You can tune it using the FILESYSTEM_UTILIZATION_BYTES environment variable. FILESYSTEM_UTILIZATION_BYTES is mutually exclusive with the FILESYSTEM_UTILIZATION_PERCENTAGE environment variable. If both FILESYSTEM_UTILIZATION_PERCENTAGE and FILESYSTEM_UTILIZATION_BYTES environment variables are set, FILESYSTEM_UTILIZATION_PERCENTAGE takes precendence.

Use the following example to tune it:

apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: VMware-io-stress
    spec:
      components:
        env:
        # Name of the VM
        - name: VM_NAME
          value: 'test-vm-01'
        # size of io to be stressed
        - name: FILESYSTEM_UTILIZATION_BYTES
          value: '1' #in GB

Mount path

It specifies the location that points to the volume mount path used in I/O stress. You can tune it using the VOLUME_MOUNT_PATH environment variable.

Use the following example to tune it:

# io-stress in the VMware VM
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: VMware-io-stress
    spec:
      components:
        env:
        # Name of the VM
        - name: VM_NAME
          value: 'test-vm-01'
        # path need to be stressed/filled
        - name: VOLUME_MOUNT_PATH
          value: '/some-dir-in-container'
        # size of io to be stressed
        - name: FILESYSTEM_UTILIZATION_BYTES
          value: '1' #in GB

Workers for stress

It specifies the worker's count for stress. You can tune it using the NUMBER_OF_WORKERS environment variable. Use the following example to tune it:

# io-stress in the VMware VM
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: VMware-io-stress
    spec:
      components:
        env:
        # Name of the VM
        - name: VM_NAME
          value: 'test-vm-01'
        # number of io workers
        - name: NUMBER_OF_WORKERS
          value: '4'
        # size of io to be stressed
        - name: FILESYSTEM_UTILIZATION_BYTES
          value: '1' #in GB