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disk-speed-limit.md

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disk io throttling

Users can add annotation to pod to limit bandwidth or IOPS.

Example: kubectl apply -f deployment.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: carina-deployment-speed-limit
  namespace: carina
  labels:
    app: web-server-speed-limit
spec:
  replicas: 1
  selector:
    matchLabels:
      app: web-server-speed-limit
  template:
    metadata:
      annotations:
        carina.storage.io/blkio.throttle.read_bps_device: "10485760"
        carina.storage.io/blkio.throttle.read_iops_device: "10000"
        carina.storage.io/blkio.throttle.write_bps_device: "10485760"
        carina.storage.io/blkio.throttle.write_iops_device: "100000"
      labels:
        app: web-server-speed-limit
    spec:
      containers:
        - name: web-server
          image: nginx:latest
          imagePullPolicy: "IfNotPresent"
          volumeMounts:
            - name: mypvc
              mountPath: /var/lib/www/html
      volumes:
        - name: mypvc
          persistentVolumeClaim:
            claimName: csi-carina-pvc-speed-limit
            readOnly: false
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: csi-carina-pvc-speed-limit
  namespace: carina
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 17Gi
  storageClassName: csi-carina-sc
  volumeMode: Filesystem

  • Carina will convert those anntoations into pod's cgroupfs hierarchy.

    cgroup v1
/sys/fs/cgroup/blkio/kubepods/burstable/pod0b0e005c-39ec-4719-bbfe-78aadbc3e4ad/blkio.throttle.read_bps_device
/sys/fs/cgroup/blkio/kubepods/burstable/pod0b0e005c-39ec-4719-bbfe-78aadbc3e4ad/blkio.throttle.read_iops_device
/sys/fs/cgroup/blkio/kubepods/burstable/pod0b0e005c-39ec-4719-bbfe-78aadbc3e4ad/blkio.throttle.write_bps_device
/sys/fs/cgroup/blkio/kubepods/burstable/pod0b0e005c-39ec-4719-bbfe-78aadbc3e4ad/blkio.throttle.write_iops_device
    cgroup v2
/sys/fs/cgroup/kubepods/burstable/pod0b0e005c-39ec-4719-bbfe-78aadbc3e4ad/io.max
  • Users can add one or more annotations. Adding or removing annotations will be synced to cgroupfs in about 60s.
  • Currently, only block device disk speed limit is supported. User can test io throttling with command dd if=/dev/zero of=out.file bs=1M count=512 oflag=dsync.
  • Carina can automatically decide whether to use cgroup v1 or cgroup v2 according to the system environment.
  • If the system uses cgroup v2, it supports buffer io speed limit (you need to enable io and memory controllers at the same time), otherwise only direct io speed limit is supported.
  • If user can set io throttling too low, it may cause the procedure of formating filesystem hangs there and then the pod will be in pending state forever.