SSD/NVMe or similar performance block device on the node for storage
We don’t recommend using spinning disks with Longhorn, due to low IOPS.
It’s recommended to run an OS from the following list for every node of your Kubernetes cluster:
OSes aren’t supported by Longhorn
Node and Disk Setup
We recommend the following setup for nodes and disks.
Use a Dedicated Disk
It’s recommended to dedicate a disk for Longhorn storage for production, instead of using the root disk.
Minimal Available Storage and Over-provisioning
If you need to use the root disk, use the default minimal available storage percentage setup which is 25%, and set overprovisioning percentage to 200% to minimize the chance of DiskPressure.
If you’re using a dedicated disk for Longhorn, you can lower the setting minimal available storage percentage to 10%.
For the Over-provisioning percentage, it depends on how much space your volume uses on average. For example, if your workload only uses half of the available volume size, you can set the Over-provisioning percentage to 200, which means Longhorn will consider the disk to have twice the schedulable size as its full size minus the reserved space.
Disk Space Management
Since Longhorn doesn’t currently support sharding between the different disks, we recommend using LVM to aggregate all the disks for Longhorn into a single partition, so it can be easily extended in the future.
Setting up Extra Disks
Any extra disks must be written in the /etc/fstab file to allow automatic mounting after the machine reboots.
Configuring Default Disks Before and After Installation
To use a directory other than the default /var/lib/longhorn for storage, the Default Data Path setting can be changed before installing the system. For details on changing pre-installation settings, refer to this section.
The Default node/disk configuration feature can be used to customize the default disk after installation. Customizing the default configurations for disks and nodes is useful for scaling the cluster because it eliminates the need to configure Longhorn manually for each new node if the node contains more than one disk, or if the disk configuration is different for new nodes. Remember to enable Create default disk only on labeled node if applicable.
If you’re using ext4 as the filesystem of the volume, we recommend adding a liveness check to workloads to help automatically recover from a network-caused interruption, a node reboot, or a Docker restart. See this section for details.
We highly recommend using the built-in backup feature of Longhorn.
For each volume, schedule at least one recurring backup. If you must run Longhorn in production without a backupstore, then schedule at least one recurring snapshot for each volume.
Longhorn system will create snapshots automatically when rebuilding a replica. Recurring snapshots or backups can also automatically clean up the system-generated snapshot.
Guaranteed Instance Manager CPU
We recommend allowing Longhorn to have CPU requests set for engine/replica manager pods.
To be precise, you can set the percentage of a node total allocatable CPU reserved for all engine/replica manager pods by modifying settings Guaranteed Engine Manager CPU and Guaranteed Replica Manager CPU.
If you want to set a concrete value (milli CPU amount) for engine/replica manager pods on a specific node, you can update the fields Engine Manager CPU Request or Replica Manager CPU Request of the node. Notice that these 2 fields will overwrite the above settings for the specific node.
The setting Guarantee Engine CPU is deprecated. For the system upgraded from old versions, Longhorn v1.1.1 will set the node fields mentioned above automatically to the same value as the deprecated setting then clean up the setting.
We don’t recommend modifying the default StorageClass named longhorn, since the change of parameters might cause issues during an upgrade later. If you want to change the parameters set in the StorageClass, you can create a new StorageClass by referring to the StorageClass examples.
Replica Node Level Soft Anti-Affinity
This setting should be set to false in production environment to ensure the best availability of the volume. Otherwise, one node down event may bring down more than one replicas of a volume.
Allow Volume Creation with Degraded Availability
This setting should be set to false in production environment to ensure every volume have the best availability when created. Because with the setting set to true, the volume creation won’t error out even there is only enough room to schedule one replica. So there is a risk that the cluster is running out of the spaces but the user won’t be made aware immediately.