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Introduction

A volume instance in Edge Infrastructure Services is a storage allocation on a node that edge applications use to store data, persist state across reboots, or share data with other applications running on the same node.

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How It Works

Diagram showing volume instances providing image storage, writable data storage, and shared data access for edge applications on a node When EVE-OS deploys an edge application to a node, it creates volume instances to provide storage for that application. A volume instance lives on the node and is tied to the node where it was created. If you want a volume to exist on multiple nodes, you create it separately on each node. There are two types of volume instances: Image Volume (Content Tree): An image volume stores an immutable application image (for example, a container image or VM disk). The image is downloaded from a datastore to the node and made available as a read-only volume. EVE-OS uses the image volume as the source when creating a running copy of an application. Image volumes are well suited for scenarios where you want to pre-stage large application images on nodes that have poor or intermittent connectivity to the storage backend. Block Storage: A block storage volume provides a mutable, writable storage space for an application. The application writes runtime data, logs, and configuration changes to the block storage volume. Block storage volumes can optionally be initialized from an existing image volume, creating a working copy of the base image on the node.

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Persistence

By default, drive storage in an edge application is non-persistent. When you run a Purge and Update operation on an application, EVE-OS wipes the drive and rebuilds it from the original source. All runtime data on that drive is permanently deleted. You can make a drive persistent by enabling the Persistent toggle on that drive in the edge application definition (in the Marketplace, in the Drives step). A persistent drive’s volume belongs to the node rather than to the application instance, and its data survives both Purge and Update operations and application deletion. See Add Persistent Volumes for configuration steps.

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Shared volumes

A single block storage volume instance can be attached to multiple edge applications running on the same node. This allows applications to read from and write to a common data source. See Attach Volumes to Multiple Applications for the configuration steps.

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Key Benefits

  • Persistent application data. Volumes retain application state across reboots and updates, preserving logs, configuration, and runtime data.
  • Efficient image pre-staging. Image volumes allow large application images to be downloaded to nodes in advance, reducing deployment time in low-bandwidth environments.
  • Data sharing between applications. Block storage volumes can be shared across multiple applications on the same node, enabling coordinated access to common datasets.
  • Per-node lifecycle management. Volumes are scoped to the node where they are created, giving you fine-grained control over storage allocation on each device.

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