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Block device performance tuning using perfProfiles

  • Feature status: Preview

Table of Contents

Summary

Azure storage publishes guidelines for the applications to configure the disks' guest OS settings to drive maximum IOPS and Bandwidth.

Azure Disk CSI driver v2 allows customers to tweak the guest OS device settings using perfProfile feature. Users can chose from a list of perfProfile to tweak the IO behavior of their block devices in accordance with their workloads.

perfProfile can be set at the StorageClass level and applies to all the disks created using the StorageClass

Perf Profiles

Today user can chose from None, Basic and Advanced perfProfile.

If no perfProfile is specified in the StorageClass, perfProfile defaults to None. Which means there will be no optimizations done for PVs created using this StorageClass.

Basic

Basic perfProfile offers a hands free option to tune the device settings for a balanced throughput and TPS workloads.

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: sc-kubestone-perf-optimized-premium-ssd-csi
provisioner: disk.csi.azure.com
parameters:
  skuName: Premium_LRS
  perfProfile: Basic # available values: "None" (default) and "Basic". The V2 driver adds "Advanced". These values are case insensitive.
reclaimPolicy: Delete
volumeBindingMode: Immediate
allowVolumeExpansion: true

Advanced

Available with v2.0.0-alpha.1+

Advanced perfProfile gives users the ultimate flexibility to tweak any device setting they desire, to optimize the disk IOs for their workload.

Device settings can be tweaked by providing overrides in the parameters section of the StorageClass, using a prefix device-setting/.

If perfProfile is set to Advanced, driver treats any parameter which starts with prefix device-setting/ as a device setting override.

Device setting overrides can be provided in format <deviceSettingPrefix><deviceSetting>: "<deviceSettingValue>".

A valid device setting override starts with device-setting/ and the deviceSetting has to be a valid block device setting in the kernel used. Relative paths to the device setting are not allowed.

For example:

To set deviceSetting /sys/block/sda/queue/scheduler (here, /sys/block/sda is an example block device) to mq-deadline, user should use below override in parameters section if StorageClass. Below is a valid device setting override.

  device-setting/queue/scheduler: "mq-deadline"

There are no limitations to how many settings user can tweak using this perfProfile.

If perfProfile is set to Advanced, at least one device setting override should be provided in the parameters.

In case, no device setting override is provided and the perfProfile is set to Advanced, CSI driver will fail any disk created using this StorageClass.

Any incorrect deviceSetting overrides provided in the parameters section will result in failure of disk staging on the node and will result in pod scheduling failure.

Here's an examples of an invalid device setting override. This override is invalid because deviceSetting uses a relative path (..). This will result in disk staging failure and cause the pod to be stuck.

  device-setting/../queue/scheduler: "mq-deadline"

Users should be careful about using advanced perfProfile and make sure they test all the deviceSetting overrides in linux kernel they plan to use.

Here's an example of a StorageClass which tweaks some well known block device settings on linux.

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: sc-kubestone-perf-optimized-premium-ssd-csi
provisioner: disk.csi.azure.com
parameters:
  skuName: Premium_LRS
  perfProfile: Advanced # available values: None(by default), Basic, Advanced. These are case insensitive.
  device-setting/queue/max_sectors_kb: "52"
  device-setting/queue/scheduler: "mq-deadline"
  device-setting/iosched/fifo_batch: "1"
  device-setting/iosched/writes_starved: "1"
  device-setting/device/queue_depth: "16"
  device-setting/queue/nr_requests: "16"
  device-setting/queue/read_ahead_kb: "8"
  device-setting/queue/wbt_lat_usec: "0"
  device-setting/queue/rotational: "0"
  device-setting/queue/nomerges: "0"
reclaimPolicy: Delete
volumeBindingMode: Immediate
allowVolumeExpansion: true

Example

Consider StorageClass sc-test-postgresql-p20-optimized in below example, which can optimize a p20 azure disk to get increased combined throughput, IOPS and better IO latency for a PostresSQL inspired fio workload.

To try the optimizations, follow below step:

  • Create an aks cluster with Standard_D4s_v4 VM SKU nodepool.

  • Install azuredisk CSI driver v2 using instructions here.

  • Install kubestone.

kustomize build github.com/xridge/kubestone/config/default?ref=v0.5.0 | sed "s/kubestone:latest/kubestone:v0.5.0/" | kubectl create -f -

kubectl create namespace kubestone
  • To run fio workload with optimized disks
cat <<EOF | kubectl apply -f -
---
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: sc-test-postgresql-p20-optimized
provisioner: disk.csi.azure.com
parameters:
  skuname: Premium_LRS
  cachingmode: None
  perfProfile: Advanced
  device-setting/queue/max_sectors_kb: "211"
  device-setting/queue/scheduler: "none"
  device-setting/device/queue_depth: "17"
  device-setting/queue/nr_requests: "44"
  device-setting/queue/read_ahead_kb: "256"
  device-setting/queue/wbt_lat_usec: "0"
  device-setting/queue/rotational: "0"
reclaimPolicy: Delete
volumeBindingMode: WaitForFirstConsumer
allowVolumeExpansion: true
---
apiVersion: perf.kubestone.xridge.io/v1alpha1
kind: Fio
metadata:
  name: test-postgresql-p20-optimized
spec:
  customJobFiles:
  - |
    [global]
    time_based=1
    ioengine=sync
    buffered=1
    runtime=120
    bs=8kiB

    [job1]
    name=checkpointer
    rw=write
    size=4GiB
    fsync_on_close=1
    sync_file_range=write:32

    [job2]
    name=wal
    rw=write
    size=2GiB
    fdatasync=1    

    [job3]
    name=large_read
    rw=read
    size=10GiB
  cmdLineArgs: --output-format=json
  podConfig:
    podLabels:
        app: kubestone
    podScheduling:
          affinity:
            podAntiAffinity:
              requiredDuringSchedulingIgnoredDuringExecution:
                - labelSelector:
                    matchExpressions:
                      - key: "app"
                        operator: In
                        values:
                        - kubestone
                  topologyKey: "kubernetes.io/hostname"
  image:
    name: xridge/fio:3.13
  volume:
    persistentVolumeClaimSpec:
      accessModes:
      - ReadWriteOnce
      resources:
        requests:
          storage: 512Gi
      storageClassName: sc-test-postgresql-p20-optimized
    volumeSource:
      persistentVolumeClaim:
        claimName: GENERATED
---
EOF
  • To run same fio workload with un-optimized disk
cat <<EOF | kubectl apply -f -
---
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: sc-test-postgresql-p20
provisioner: disk.csi.azure.com
parameters:
  cachingmode: None
  skuname: Premium_LRS
  perfProfile: None
reclaimPolicy: Delete
volumeBindingMode: WaitForFirstConsumer
allowVolumeExpansion: true
---
apiVersion: perf.kubestone.xridge.io/v1alpha1
kind: Fio
metadata:
  name: test-postgresql-p20
spec:
  customJobFiles:
  - |
    [global]
    time_based=1
    ioengine=sync
    buffered=1
    runtime=120
    bs=8kiB

    [job1]
    name=checkpointer
    rw=write
    size=4GiB
    fsync_on_close=1
    sync_file_range=write:32

    [job2]
    name=wal
    rw=write
    size=2GiB
    fdatasync=1    

    [job3]
    name=large_read
    rw=read
    size=10GiB
  cmdLineArgs: --output-format=json
  podConfig:
    podLabels:
        app: kubestone
    podScheduling:
          affinity:
            podAntiAffinity:
              requiredDuringSchedulingIgnoredDuringExecution:
                - labelSelector:
                    matchExpressions:
                      - key: "app"
                        operator: In
                        values:
                        - kubestone
                  topologyKey: "kubernetes.io/hostname"
  image:
    name: xridge/fio:3.13
  volume:
    persistentVolumeClaimSpec:
      accessModes:
      - ReadWriteOnce
      resources:
        requests:
          storage: 512Gi
      storageClassName: sc-test-postgresql-p20
    volumeSource:
      persistentVolumeClaim:
        claimName: GENERATED
---
EOF
  • To uninstall kubestone
kubectl delete namespace kubestone --ignore-not-found

kustomize build github.com/xridge/kubestone/config/default?ref=v0.5.0 | sed "s/kubestone:latest/kubestone:v0.5.0/" | kubectl delete --ignore-not-found -f -
  • To delete StorageClass
kubectl delete sc sc-test-postgresql-p20 --ignore-not-found

kubectl delete sc sc-test-postgresql-p20-optimized --ignore-not-found
  • To uninstall azuredisk CSI driver v2 use instructions here

Limitations

  • This feature is not supported for HDD or UltraDisk right now.
  • This feature only optimizes data disks (PVs). Local/temp disks on the VM are not optimized by this feature.
  • The current implementation only optimizes the disks which use the storVsc linux disk driver.

Caution

  • This feature is currently in alpha and customers are advised to not use this feature in their production workloads.
  • Device tuned using the Basic and Advanced perfProfile options can show variance in performance due to several factors including (but not limited to) disk size, VM SKU, disk caching mode, linux distribution and kernel version, workload type. Customers are advised to test the perfProfile they chose in the controlled environment to ascertain the performance benefits, before using them.