I'm working with a persistent volume set to ReadWriteMany, and I've got about 100 MB of data stored on it using NFS. I'm curious about how the synchronization works: if one of my pods updates something in the volume, how do the other pods become aware of this change? When they do realize an update has happened, do they reload the whole volume into memory, or just the parts that changed?
2 Answers
The pods actually don't inherently know about the changes. NFS has its own locking mechanism which can be quite intricate. The applications running in your containers don’t need to be aware of NFS specifically, but keep in mind that if you're trying to modify the same file from multiple instances of an app, that can lead to issues. You'll need to implement a way to handle file modifications intelligently by using methods to check for changes, like using the `stat` syscall. If you're running into this kind of issue, you might want to consider whether NFS is the right choice and if a database might be more appropriate.
That's the way NFS operates—it’s like a shared drive. When a file gets updated, all the other pods mounted to that NFS can see the changes immediately. Kubernetes itself isn't doing anything special here; it’s really just leveraging the NFS capabilities.
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