Shulou(Shulou.com)06/01 Report--

Today, I will talk to you about how to verify the persistence of Swarm data. Many people may not know much about it. In order to make you understand better, the editor has summarized the following for you. I hope you can get something according to this article.

Scale Up

Add a copy:

Docker service update-replicas 2 my_web

Before running, let's speculate that the ideal result would be that swarm starts a second copy on swarm-worker2, and volume my_web will also be mounted.

Compare the actual running results:

There's a little bit of complication:

Swarm first tried to start the second copy on swarm-worker2, but failed on mount volume.

I tried again three times and failed.

Finally, the second copy is successfully launched in swarm-worker1.

The reason for mount failure is that Rex-Ray volume with VirtualBox as backend does not support attach to multiple Host at the same time.

It is important to note that this is actually a limitation of VirtualBox, not Rex-Ray. There is no problem if backend chooses Ceph RBD.

Update Volume

Update the contents of volume.

Service returns the updated content, and the data has been synchronized to the copy.

Failover

Now simulate the failure situation. The shutdown node swarm-worker1, and after a while, all replicas will be migrated to swarm-worker2.

Visit service and the previously updated content remains intact.

As a storage orchestration scheme of Swarm, Rex-Ray can well support cross-host volume management, and volume can also migrate automatically when containers are migrated in a cluster.

After reading the above, do you have any further understanding of how to verify Swarm data persistence? If you want to know more knowledge or related content, please follow the industry information channel, thank you for your support.

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