I am trying to be more familiar with Kubernetes orchestration tool and I faced a conceptual issue in case of volumes. From my understanding, a volume allocates a space on the drive in order to persist data and this volume can be mount on a pod. This is ok until now. But what will happen in the scenario below: We have 3 pods and each of them has mounted volume which we persist some data. In some time we don't need 3 pods anymore and we kill one of them. What about its volume and its data? These data will be lost or should we transfer these data somehow to another volume?
Sorry for this bad definition, but I am trying to understand. Thanks in advance!
A Volume is a way to describe a place where data can be stored. It does not hae to be on a local drive, it does not have to be a network block storage. A whole bunch of volume implementations are available ranging from emptyDir, hostPath, via iSCSI, EBS all the way to NFS or GlusterFS. A volume is a place where you define a piece of more or less posix compliant filesystem.
What happens with it when it's pod is gone is mostly up to what you are using. For example EBS volume can be scraped but NFS share may stay exactly as it was.
There is even more, as you can have Persistent Volume Claims, Volume Claim Templates and Persistent Volumes, which all build up upon the Volume concept it self to provide usefull abstractions.
I strongly encurage you to read and play with all of them to get better understanding of how storage can be managed in Kubernetes.