Hi Oliver,

Generally, each unique ISC_DATA_DIRECTORY should be bound to one persistent instance.  If you have two instances you wish to maintain, IRIS1 and IRIS2, they should each have their own unique persistent storage location.  There's nothing preventing you from putting both of them on the same EFS store, as long as that point to different, unique directories within that store.  So your idea of an individual directory tree for each container should work just fine.  (Exception: If you are using mirroring for availability, I would not recommend storing both/all parts of a given mirror set on the same EFS store.)  Two simultaneously running containers/instances should never be pointing at the same mgr/IRIS.DAT, that will not result in a functional application.

I say persistent instance because you can freely stop a container, and then start a new one with the same ISC_DATA_DIRECTORY and have a new container - possibly with a newer version of InterSystems IRIS, or a newer version of your code - run on the same persisted data.

Additionally: Depending on your particular needs, you may not wish to use EFS for ISC_DATA_DIRECTORY locations.  EFS is an NFS implementation, which has been known to cause problems with container runtime engines, and EFS will generally have higher disk latency than other things, EBS might be one better choice.  Consult AWS documentation to be sure!  https://docs.aws.amazon.com/efs/latest/ug/performance.html