Settings Reference

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Customizing Default Settings

To configure Longhorn before installing it, see this section for details.

General

Allow Node Drain with the Last Healthy Replica

Default: false

By default, Longhorn will block kubectl drain action on a node if the node contains the last healthy replica of a volume.

If this setting is enabled, Longhorn will not block kubectl drain action on a node even if the node contains the last healthy replica of a volume.

Automatically Cleanup System Generated Snapshot

Default: true

Longhorn will generate system snapshot during replica rebuild, and if a user doesn’t setup a recurring snapshot schedule, all the system generated snapshots would be left in the replica, and user has to delete them manually, this setting allow Longhorn to automatically cleanup system generated snapshot after replica rebuild.

Automatically Delete Workload Pod when The Volume Is Detached Unexpectedly

Default: true

If enabled, Longhorn will automatically delete the workload pod that is managed by a controller (e.g. deployment, statefulset, daemonset, etc…) when Longhorn volume is detached unexpectedly (e.g. during Kubernetes upgrade, Docker reboot, or network disconnect). By deleting the pod, its controller restarts the pod and Kubernetes handles volume reattachment and remount.

If disabled, Longhorn will not delete the workload pod that is managed by a controller. You will have to manually restart the pod to reattach and remount the volume.

Note: This setting doesn’t apply to the workload pods that don’t have a controller. Longhorn never deletes them.

Automatic Salvage

Default: true

If enabled, volumes will be automatically salvaged when all the replicas become faulty e.g. due to network disconnection. Longhorn will try to figure out which replica(s) are usable, then use them for the volume.

Concurrent Automatic Engine Upgrade Per Node Limit

Default: 0

This setting controls how Longhorn automatically upgrades volumes’ engines to the new default engine image after upgrading Longhorn manager. The value of this setting specifies the maximum number of engines per node that are allowed to upgrade to the default engine image at the same time. If the value is 0, Longhorn will not automatically upgrade volumes’ engines to default version.

Create Default Disk on Labeled Nodes

Default: false

If no other disks exist, create the default disk automatically, only on nodes with the Kubernetes label node.longhorn.io/create-default-disk=true .

If disabled, the default disk will be created on all new nodes when the node is detected for the first time.

This option is useful if you want to scale the cluster but don’t want to use storage on the new nodes, or if you want to customize disks for Longhorn nodes.

Custom mkfs.ext4 parameters

Allows setting additional filesystem creation parameters for ext4. For older host kernels it might be necessary to disable the optional ext4 metadata_csum feature by specifying -O ^64bit,^metadata_csum.

Custom Resource API Version

Default: longhorn.io/v1beta1

The current customer resource’s API version, e.g. longhorn.io/v1beta1. Set by manager automatically.

Default Data Locality

Default: disabled

We say a Longhorn volume has data locality if there is a local replica of the volume on the same node as the pod which is using the volume. This setting specifies the default data locality when a volume is created from the Longhorn UI. For Kubernetes configuration, update the dataLocality in the StorageClass

The available modes are:

  • disabled. This is the default option. There may or may not be a replica on the same node as the attached volume (workload).

  • best-effort. This option instructs Longhorn to try to keep a replica on the same node as the attached volume (workload). Longhorn will not stop the volume, even if it cannot keep a replica local to the attached volume (workload) due to environment limitation, e.g. not enough disk space, incompatible disk tags, etc.

Default Data Path

Default: /var/lib/longhorn/

Default path to use for storing data on a host.

Can be used with Create Default Disk on Labeled Nodes option, to make Longhorn only use the nodes with specific storage mounted at, for example, /opt/longhorn when scaling the cluster.

Default Engine Image

The default engine image used by the manager. Can be changed on the manager starting command line only.

Every Longhorn release will ship with a new Longhorn engine image. If the current Longhorn volumes are not using the default engine, a green arrow will show up, indicate this volume needs to be upgraded to use the default engine.

Default Instance Manager Image

The default instance manager image used by the manager. Can be changed on the manager starting command line only.

Default Longhorn Static StorageClass Name

Default: longhorn-static

The storageClassName is for persistent volumes (PVs) and persistent volume claims (PVCs) when creating PV/PVC for an existing Longhorn volume. Notice that it’s unnecessary for users to create the related StorageClass object in Kubernetes since the StorageClass would only be used as matching labels for PVC bounding purpose. By default ‘longhorn-static’.

Default Replica Count

Default: 3

The default number of replicas when creating the volume from Longhorn UI. For Kubernetes, update the numberOfReplicas in the StorageClass

The recommended way of choosing the default replica count is: if you have three or more nodes for storage, use 3; otherwise use 2. Using a single replica on a single node cluster is also OK, but the high availability functionality wouldn’t be available. You can still take snapshots/backups of the volume.

Default Share Manager Image

The default instance manager image used by the manager. Can be changed on the manager starting command line only.

Disable Revision Counter

Default: false

Allows engine controller and engine replica to disable revision counter file update for every data write. This improves the data path performance. See Revision Counter for details.

Enable Upgrade Checker

Default: true

Upgrade Checker will check for a new Longhorn version periodically. When there is a new version available, it will notify the user in the Longhorn UI.

Latest Longhorn Version

The latest version of Longhorn available. Automatically updated by the Upgrade Checker.

Only available if Upgrade Checker is enabled.

Pod Deletion Policy When Node is Down

Default: do-nothing

Defines the Longhorn action when a Volume is stuck with a StatefulSet/Deployment Pod on a node that is down.

  • do-nothing is the default Kubernetes behavior of never force deleting StatefulSet/Deployment terminating pods. Since the pod on the node that is down isn’t removed, Longhorn volumes are stuck on nodes that are down.
  • delete-statefulset-pod Longhorn will force delete StatefulSet terminating pods on nodes that are down to release Longhorn volumes so that Kubernetes can spin up replacement pods.
  • delete-deployment-pod Longhorn will force delete Deployment terminating pods on nodes that are down to release Longhorn volumes so that Kubernetes can spin up replacement pods.
  • delete-both-statefulset-and-deployment-pod Longhorn will force delete StatefulSet/Deployment terminating pods on nodes that are down to release Longhorn volumes so that Kubernetes can spin up replacement pods.

Registry Secret

The Kubernetes Secret name.

Replica Replenishment Wait Interval

Default: 600

When there is at least one failed replica volume in a degraded volume, this interval in seconds determines how long Longhorn will wait at most in order to reuse the existing data of the failed replicas rather than directly creating a new replica for this volume.

Warning: This wait interval works only when there is at least one failed replica in the volume. And this option may block the rebuilding for a while.

System Managed Pod Image Pull Policy

Default: if-not-present

This setting defines the Image Pull Policy of Longhorn system managed pods, e.g. instance manager, engine image, CSI driver, etc.

Notice that the new Image Pull Policy will only apply after the system managed pods restart.

This setting definition is exactly the same as that of in Kubernetes. Here are the available options:

  • always. Every time the kubelet launches a container, the kubelet queries the container image registry to resolve the name to an image digest. If the kubelet has a container image with that exact digest cached locally, the kubelet uses its cached image; otherwise, the kubelet downloads (pulls) the image with the resolved digest, and uses that image to launch the container.

  • if-not-present. The image is pulled only if it is not already present locally.

  • never. The image is assumed to exist locally. No attempt is made to pull the image.

Backing Image Cleanup Wait Interval

Default: 60

This interval in minutes determines how long Longhorn will wait before cleaning up the backing image file when there is no replica in the disk using it.

Backing Image Recovery Wait Interval

Default: 300

The interval in seconds determines how long Longhorn will wait before re-downloading the backing image file when all disk files of this backing image become failed or unknown.

Note:

  • This recovery only works for the backing image of which the creation type is download.
  • File state unknown means the related manager pods on the pod is not running or the node itself is down/disconnected.

Backups

Allow Recurring Job While Volume Is Detached

Default: false

If this setting is enabled, Longhorn automatically attaches the volume and takes snapshot/backup when it is the time to do recurring snapshot/backup.

Note that during the time the volume was attached automatically, the volume is not ready for the workload. the workload will have to wait until the recurring job finishes.

Backup Target

Example: s3://backupbucket@us-east-1/backupstore

The target used for backup. NFS and S3 are supported. See Setting a Backup Target for details.

Backup Target Credential Secret

Example: s3-secret

The Kubernetes secret associated with the backup target. See Setting a Backup Target for details.

Backupstore Poll Interval

Default: 300

The interval in seconds to poll the backup store for updating volumes’ Last Backup field. Set to 0 to disable the polling. See Setting up Disaster Recovery Volumes for details.

For more information on how the backupstore poll interval affects the recovery time objective and recovery point objective, refer to the concepts section.

Scheduling

Allow Volume Creation with Degraded Availability

Default: true

This setting allows user to create and attach a volume that doesn’t have all the replicas scheduled at the time of creation.

Note: It’s recommended to disable this setting when using Longhorn in the production environment. See Best Practices for details.

Disable Scheduling On Cordoned Node

Default: true

When this setting is checked, the Longhorn Manager will not schedule replicas on Kubernetes cordoned nodes.

When this setting is un-checked, the Longhorn Manager will schedule replicas on Kubernetes cordoned nodes.

Replica Node Level Soft Anti-Affinity

Default: false

When this setting is checked, the Longhorn Manager will allow scheduling on nodes with existing healthy replicas of the same volume.

When this setting is un-checked, the Longhorn Manager will not allow scheduling on nodes with existing healthy replicas of the same volume.

Replica Zone Level Soft Anti-Affinity

Default: true

When this setting is checked, the Longhorn Manager will allow scheduling new replicas of a volume to the nodes in the same zone as existing healthy replicas.

When this setting is un-checked, Longhorn Manager will not allow scheduling new replicas of a volume to the nodes in the same zone as existing healthy replicas.

Note:

  • Nodes that don’t belong to any zone will be treated as if they belong to the same zone.
  • Longhorn relies on label topology.kubernetes.io/zone=<Zone name of the node> in the Kubernetes node object to identify the zone.

Replica Auto Balance

Default: disabled

Enable this setting automatically rebalances replicas when discovered an available node.

The available global options are:

  • disabled. This is the default option. No replica auto-balance will be done.

  • least-effort. This option instructs Longhorn to balance replicas for minimal redundancy.

  • best-effort. This option instructs Longhorn try to balancing replicas for even redundancy. Longhorn does not forcefully re-schedule the replicas to a zone that does not have enough nodes to support even balance. Instead, Longhorn will re-schedule to balance at the node level.

Longhorn also supports customizing for individual volume. The setting can be specified in UI or with Kubernetes manifest volume.spec.replicaAutoBalance, this overrules the global setting. The available volume spec options are:

Default: ignored

  • ignored. This is the default option that instructs Longhorn to inherit from the global setting.

  • disabled. This option instructs Longhorn no replica auto-balance should be done.”

  • least-effort. This option instructs Longhorn to balance replicas for minimal redundancy.

  • best-effort. This option instructs Longhorn to try balancing replicas for even redundancy. Longhorn does not forcefully re-schedule the replicas to a zone that does not have enough nodes to support even balance. Instead, Longhorn will re-schedule to balance at the node level.

Storage Minimal Available Percentage

Default: 25

With the default setting of 25, the Longhorn Manager will allow scheduling new replicas only after the amount of disk space has been subtracted from the available disk space (Storage Available) and the available disk space is still over 25% of actual disk capacity (Storage Maximum). Otherwise the disk becomes unschedulable until more space is freed up.

See Multiple Disks Support for details.

Storage Over Provisioning Percentage

Default: 200

The over-provisioning percentage defines how much storage can be allocated relative to the hard drive’s capacity.

With the default setting of 200, the Longhorn Manager will allow scheduling new replicas only after the amount of disk space has been added to the used disk space (storage scheduled), and the used disk space (Storage Maximum - Storage Reserved) is not over 200% of the actual usable disk capacity.

This value can be lowered to avoid overprovisioning storage. See Multiple Disks Support for details. Also, a replica of volume may take more space than the volume’s size since the snapshots need storage space as well. The users can delete snapshots to reclaim spaces.

Danger Zone

Concurrent Replica Rebuild Per Node Limit

Default: 5

This setting controls how many replicas on a node can be rebuilt simultaneously.

Typically, Longhorn can block the replica starting once the current rebuilding count on a node exceeds the limit. But when the value is 0, it means disabling the replica rebuilding.

WARNING:

  • The old setting “Disable Replica Rebuild” is replaced by this setting.
  • Different from relying on replica starting delay to limit the concurrent rebuilding, if the rebuilding is disabled, replica object replenishment will be directly skipped.
  • When the value is 0, the eviction and data locality feature won’t work. But this shouldn’t have any impact to any current replica rebuild and backup restore.

Guaranteed Engine Manager CPU

Default: 12

This integer value indicates what percentage of the total allocatable CPU on each node will be reserved for each engine manager Pod. For example, 10 means 10% of the total CPU on a node will be allocated to each engine manager pod on this node. This will help maintain engine stability during high node workload.

In order to prevent an unexpected volume engine crash as well as guarantee a relatively acceptable I/O performance, you can use the following formula to calculate a value for this setting:

Guaranteed Engine Manager CPU = The estimated max Longhorn volume engine count on a node * 0.1 / The total allocatable CPUs on the node * 100.

The result of above calculation doesn’t mean that’s the maximum CPU resources the Longhorn workloads require. To fully exploit the Longhorn volume I/O performance, you can allocate/guarantee more CPU resources via this setting.

If it’s hard to estimate the usage now, you can leave it with the default value, which is 12%. Then you can tune it when there is no running workload using Longhorn volumes.

Warning:

  • Value 0 means removing the CPU requests from spec of engine manager pods.
  • Considering the possible number of new instance manager pods in a further system upgrade, this integer value ranges from 0 to 40. And the total combined with the setting ‘Guaranteed Replica Manager CPU’ should not be greater than 40.
  • One more set of instance manager pods may need to be deployed when the Longhorn system is upgraded. If current available CPUs of the nodes are not enough for the new instance manager pods, you need to detach the volumes using the oldest instance manager pods so that Longhorn can clean up the old pods automatically and release the CPU resources. And the new pods with the latest instance manager image will be launched then.
  • This global setting will be ignored for a node if the field “EngineManagerCPURequest” on the node is set.
  • After this setting is changed, all engine manager pods using this global setting on all the nodes will be automatically restarted. In other words, DO NOT CHANGE THIS SETTING WITH ATTACHED VOLUMES.

Guaranteed Replica Manager CPU

Default: 12

Similar to “Guaranteed Engine Manager CPU”, this integer value indicates what percentage of the total allocatable CPU on each node will be reserved for each replica manager Pod. For example, 10 means 10% of the total CPU on a node will be allocated to each replica manager pod on this node. This will help maintain replica stability during high node workload.

In order to prevent an unexpected volume replica crash as well as guarantee a relatively acceptable IO performance, you can use the following formula to calculate a value for this setting:

Guaranteed Replica Manager CPU = The estimated max Longhorn volume replica count on a node * 0.1 / The total allocatable CPUs on the node * 100.

The result of above calculation doesn’t mean that’s the maximum CPU resources the Longhorn workloads require. To fully exploit the Longhorn volume I/O performance, you can allocate/guarantee more CPU resources via this setting.

If it’s hard to estimate the usage now, you can leave it with the default value, which is 12%. Then you can tune it when there is no running workload using Longhorn volumes.

Warning:

  • Value 0 means removing the CPU requests from specs of replica manager pods.
  • Considering the possible number of new instance manager pods in a further system upgrade, this integer value ranges from 0 to 40. And the total combined with the setting ‘Guaranteed Engine Manager CPU’ should not be greater than 40.
  • One more set of instance manager pods may need to be deployed when the Longhorn system is upgraded. If current available CPUs of the nodes are not enough for the new instance manager pods, you need to detach the volumes using the oldest instance manager pods so that Longhorn can clean up the old pods automatically and release the CPU resources. And the new pods with the latest instance manager image will be launched then.
  • This global setting will be ignored for a node if the field “ReplicaManagerCPURequest” on the node is set.
  • After this setting is changed, all replica manager pods using this global setting on all the nodes will be automatically restarted. In other words, DO NOT CHANGE THIS SETTING WITH ATTACHED VOLUMES.

Kubernetes Taint Toleration

Example: nodetype=storage:NoSchedule

If you want to dedicate nodes to just store Longhorn replicas and reject other general workloads, you can set tolerations for all Longhorn components and add taints to the nodes dedicated for storage.

Longhorn system contains user deployed components (e.g, Longhorn manager, Longhorn driver, Longhorn UI) and system managed components (e.g, instance manager, engine image, CSI driver, etc.) This setting only sets taint tolerations for system managed components. Depending on how you deployed Longhorn, you need to set taint tolerations for user deployed components in Helm chart or deployment YAML file.

All Longhorn volumes should be detached before modifying toleration settings. We recommend setting tolerations during Longhorn deployment because the Longhorn system cannot be operated during the update.

Multiple tolerations can be set here, and these tolerations are separated by semicolon. For example:

  • key1=value1:NoSchedule; key2:NoExecute
  • : this toleration tolerates everything because an empty key with operator Exists matches all keys, values and effects
  • key1=value1: this toleration has empty effect. It matches all effects with key key1 See Taint Toleration for details.

Priority Class

Example: high-priority

By default, Longhorn workloads run with the same priority as other pods in the cluster, meaning in cases of node pressure, such as a node running out of memory, Longhorn workloads will be at the same priority as other Pods for eviction.

The Priority Class setting will specify a Priority Class for the Longhorn workloads to run as. This can be used to set the priority for Longhorn workloads higher so that they will not be the first to be evicted when a node is under pressure.

Longhorn system contains user deployed components (e.g, Longhorn manager, Longhorn driver, Longhorn UI) and system managed components (e.g, instance manager, engine image, CSI driver, etc.) Note that this setting only sets Priority Class for system managed components. Depending on how you deployed Longhorn, you need to set Priority Class for user deployed components in Helm chart or deployment YAML file.

Warning: This setting should only be changed after detaching all Longhorn volumes, as the Longhorn system components will be restarted to apply the setting. The Priority Class update will take a while, and users cannot operate Longhorn system during the update. Hence, it’s recommended to set the Priority Class during Longhorn deployment.

See Priority Class for details.

System Managed Components Node Selector

Example: label-key1:label-value1;label-key2:label-value2

If you want to restrict Longhorn components to only run on a particular set of nodes, you can set node selector for all Longhorn components.

Longhorn system contains user deployed components (e.g, Longhorn manager, Longhorn driver, Longhorn UI) and system managed components (e.g, instance manager, engine image, CSI driver, etc.) You need to set node selector for both of them. This setting only sets node selector for system managed components. Follow the instruction at Node Selector to change node selector.

Warning: Since all Longhorn components will be restarted, the Longhorn system is unavailable temporarily. Make sure all Longhorn volumes are detached. If there are running Longhorn volumes in the system, this means the Longhorn system cannot restart its components and the request will be rejected. Don’t operate the Longhorn system while node selector settings are updated and Longhorn components are being restarted.

Deprecated

Guaranteed Engine CPU

Default:

This deprecated setting is replaced by 2 new settings “Guaranteed Engine Manager CPU” and “Guaranteed Replica Manager CPU” since Longhorn version v1.1.1.

Disable Replica Rebuild

Default: false

This deprecated setting is replaced by the new setting ‘Concurrent Replica Rebuild Per Node Limit’. Once the new setting value is 0, it means rebuilding disable.

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