Node-specific Volume Limits
This page describes the maximum number of volumes that can be attached to a node for various cloud providers.
Cloud providers like Google, Amazon, and Microsoft typically have a limit on how many volumes can be attached to a node. It is important for Kubernetes to respect those limits. Otherwise, Pods scheduled on a node could get stuck waiting for volumes to attach.
Kubernetes default limits
The Kubernetes scheduler has default limits on the number of volumes that can be attached to a node:
| Cloud service | Maximum volumes per node |
|---|---|
| Amazon Elastic Block Store (EBS) | 39 |
| Google Persistent Disk | 16 |
| Microsoft Azure Disk Storage | 16 |
Custom limits
You can change these limits by setting the value of the
KUBE_MAX_PD_VOLS environment variable, and then starting the scheduler.
Use caution if you set a limit that is higher than the default limit. Consult the cloud provider’s documentation to make sure that nodes can actually support the limit you set.
The limit applies to the entire cluster, so it affects all nodes.
Dynamic volume limits
FEATURE STATE:
Kubernetes v1.11
alpha
This feature is currently in a alpha state, meaning:
- The version names contain alpha (e.g. v1alpha1).
- Might be buggy. Enabling the feature may expose bugs. Disabled by default.
- Support for feature may be dropped at any time without notice.
- The API may change in incompatible ways in a later software release without notice.
- Recommended for use only in short-lived testing clusters, due to increased risk of bugs and lack of long-term support.
Kubernetes 1.11 introduces dynamic volume limits based on node type. This is an alpha feature that supports these services:
- Amazon EBS
- Google Persistent Disk
To enable dynamic volume limits, set the AttachVolumeLimit
feature gate
to True.
When the dynamic volume limits feature is enabled, Kubernetes automatically determines the node type and supports the appropriate number of attachable volumes for the node. For example:
On Google Compute Engine, up to 128 volumes could be attached to a node, depending on the node type.
For Amazon EBS disks on M5/C5 instance types, Kubernetes would permit only 25 volumes to be attached to a node. For other instance types on Amazon Elastic Compute Cloud (EC2), Kubernetes would permit 39 volumes to be attached.