Docker volumes allow storing state from containers outside of the image layer for persistence. They can be local storage or enabled for external storage management using plugins. This provides high availability for data by allowing the data to move with containers during failures or maintenance. The document discusses key concepts around stateful vs stateless containers and volumes. It also demonstrates creating and managing volumes using Docker Volume plugins in UCP for shared storage and failover capabilities.

1. Everything you need to know
about Docker and storage.
Ryan
Wallner
Technical Evangelist,
ClusterHQ

2. Key Concepts
Stateful vs Stateless
Volumes
Plugins
Agenda
Volumes & UCP
UCP + Volumes
External Volumes
VolumeHub
Demo
Creating Volumes
Manage Volumes
Workloads

3. Key Concepts
Docker & Storage

4. Docker + Storage

5. "Stateful" Container
• Secrets - public/private keys,
password, etc
• Databases - databases, sharded,
clustered.
• Logs - to collect support bundles, run
analytics for data mining, etc.
• Other - CI repo data, transcoded
bits...
Stateful vs. Stateless
"Stateless" Container
• Nothing to Disk
• Web Front-End
• Can stop and start as many
containers as you’d like
• Like http is stateless
• Container is ephemeral
• What has happened or changed will
be lost.

6. Docker volumes help store state from
the application to locations outside the
docker image layer. They are logical
building blocks for shared storage
when combined with plugins.
• Data is local to engine host only.
• Bind-mounts also local, bypass
UFS.
• Data is inflexible, prone to loss.
Docker Volumes
$ docker run
--name my-special-container
-v /container/dir busybox
[{e779eb1/var/lib/docker/volumes/e779eb1/_
data /container/dir local true }]

7. Enable external storage management
such as shared-storage for volumes.
• Data is external to engine host.
• Enables HA for data.
• Data can move with container on
failure, maintenance etc.
Docker Volume
Plugins

8. Example
$ docker run --name database
--volume-driver flocker
-v vol:/data redis
database
$ docker inspect -f “{{.Mounts}}” database
[{vol /flocker/71887326.. /data flocker rw true rprivate}]

9. Container Movement

10. Volumes & UCP
Docker & Storage

11. Volumes in UCP
• Create, Delete, Use from UI
• Takes advantage of volume
drivers.
• Limited view into volume
management

12. VolumeHub
• Clear visibility for volume
management.
• Current status of volumes and
their operations.
• Searchable name and metadata.
• How much storage in use by size
of volumes.

14. Demo

15. Demo Intro
$ docker volume create
-d flocker --name testfailover
-o size=10G
$ docker run -d --name=redis-server
--volume-driver=flocker -v testfailover:/data
-e reschedule:on-node-failure -e constraint:node!=mha-demo2
redis redis-server --appendonly yes

16. Container running in UCP.

17. Simulate a Failure

18. Container Re-scheduling

19. Thank you!