Attach Volumes to Multiple Applications

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Introduction

This procedure explains how to share a volume between multiple edge applications running on the same node. Shared volumes are useful when multiple applications need access to the same dataset, such as sensor readings, log files, or configuration files. EVE-OS (Edge Virtualization Engine) implements shared volume access using the Plan 9 filesystem protocol. All applications that mount the volume can read from and write to a single, consistent data source. Virtual machine (VM) workloads must mount shared volumes manually inside the guest OS using the preferred method for that OS. Container-based applications mount the volume automatically at the path you specify during application configuration.

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Prerequisites

• EVE-OS 12.7.0 or later on the target node.
• You have the SysManager or SysAdmin role in your enterprise. See Manage Roles.
• At least one node onboarded to Edge Infrastructure Services.

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Create an Image Volume

The shared block storage volume requires a base image volume to initialize from. Create the image volume first.

1. In the sidebar, click Infrastructure > Workloads > Volumes.
2. Click the Add button (floating button in the lower right of the page).
3. Select Image Volume and click Next.
4. In the Identity section, enter a name, title, and optional description. Select the target node.
5. In the Storage section, select the App Image you want to use as the base. Choose a container image if you plan to allow multiple applications to write to the shared volume. VM disk formats (QCOW2, RAW, ISO) support only read-only sharing across multiple applications.
6. Click Create Volume.

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Create a Block Storage Volume

Create the block storage volume on the same node and link it to the image volume created in the previous step.

1. In the sidebar, click Infrastructure > Workloads > Volumes.
2. Click the Add button (floating button in the lower right of the page).
3. Select Block Storage and click Next.
4. In the Identity section, enter a name, title, and optional description. Select the same node where you created the image volume.
5. In the Storage section:
   • Set the Access Mode based on your sharing requirements:
     • Read Only: All applications can read from the volume but cannot write to it.
     • Read Write: All applications can read from and write to the volume.
     • Multi Read / Single Write: Behaves the same as Read Write.
   • Set the Max Size to a value larger than the size of the base container image.
   • In the Image Volume field, select the image volume you created in the previous step. This initializes the block storage volume from the base image.
   • Note the value you enter in the Name field. You will use it as the volume label when configuring application drives.
6. Click Create Volume.

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Create and Configure Edge Applications

For each application that will share the volume, configure the application’s drives to reference the block storage volume.

1. Create or edit the edge application definition. See Create and Manage an App Image for instructions.
2. In the Drives section of the application, add an additional drive.
3. In the Tag field for the additional drive, enter the Name of the block storage volume you created. This tag is how EVE-OS maps the drive definition to the actual volume instance on the node.
4. In the Mount Path field, specify the path inside the application’s filesystem where the volume will be mounted (for example, /data/shared).
5. Repeat these steps for each application that should share the volume.

Note that the first drive in an application definition typically maps to the application’s primary image, which does not require a tag. The shared volume is the additional drive, and it is the one that requires the tag.

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Deploy the Application Instances

Deploy all application instances to the node where you created the volumes. See Deploy an Application Instance for the deployment wizard walkthrough. After deployment, all applications with the matching drive tag mount the volume at the path you specified. Applications can read from and write files to the mounted path, and those files are accessible to all other applications that share the volume.

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Verify the Configuration

After deployment, navigate to the volume detail page and click the Used by tab. Confirm that all expected application instances appear in the list. To verify that data sharing is working, check that a file written by one application is visible to the other applications mounting the same volume.

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Next Steps