3

I need a shared volume accessible from multiple pods for caching files in RAM on each node.

The problem is that the emptyDir volume provisioner (which supports Memory as its medium) is available in Volume spec but not in PersistentVolume spec.

Is there any way to achieve this, except by creating a tmpfs volume manually on each host and mounting it via local or hostPath provisioner in the PV spec?

Note that Docker itself supports such volumes:

docker volume create --driver local --opt type=tmpfs --opt device=tmpfs \
       --opt o=size=100m,uid=1000 foo

I don't see any reason why k8s doesn't. Or maybe it does, but it's not obvious?

I tried playing with local and hostPath PVs with mountOptions but it didn't work.

Adam
  • 2,897
  • 2
  • 23
  • 23

1 Answers1

1

EmtpyDir tied to lifetime of a pod, so it can't be used via shared with multiple pods. What you request, is additional feature and if you look at below github discussions, you will see that you are not the first that asking for this feature.

consider a tmpfs storage class

Also according your mention that docker supports this tmpfs volume, yes it supports, but you can't share this volume between containers. From Documentation

Limitations of tmpfs mounts:

Unlike volumes and bind mounts, you can’t share tmpfs mounts between containers.

Community
  • 1
  • 1
clxoid
  • 2,577
  • 12
  • 21
  • 1
    Regarding Docker: `foo` is a volume, so it can be shared between containers. I've checked and it works. – Adam Mar 14 '19 at 16:05