Som standard er data i en container kortlevet — forsvinner når containeren fjernes. Volumer (og bind mounts) gir persistent lagring som overlever containere, essensielt for databaser og data som må overleve containeromstarter/fjerninger.
Problemet: containere er kortlevede
A container's writable layer is DELETED when the container is removed:
→ data written inside the container (e.g. a database's files) is LOST
→ containers are meant to be disposable/replaceable → don't store important data in them
→ For persistent data, you need storage OUTSIDE the container's lifecycle.
