Clarify that RWX filesystem volumes require migratable=false with dataEngine=v2

[glovecchi0]

Problem:

When migratable=true is set, Longhorn creates a migratable RWX block volume intended for VM live migration workflows instead of a standard RWX filesystem volume.

As a result, the standard RWX filesystem sharing mechanism based on Longhorn share-manager and NFS is not used, and RWX filesystem volumes do not function as expected.

Solution:

Do not use migratable=true for standard RWX filesystem volumes. Ensure migratable is unset or explicitly set to false to enable the Longhorn share-manager and NFS-based RWX filesystem sharing layer.

[glovecchi0]

CC: @Vicente-Cheng , @Martin-Weiss

[Vicente-Cheng]

I thought maybe we could remove this line. Just keeping the user informed that the migratable=true would not create the RWX filesystem volume should be enough.
WDYT?

(Please apply with the following versioned document)

[glovecchi0]

Deleted the first 2 sentences.

Thank you, @Vicente-Cheng !

[jillian-maroket]

Review done. Please apply the suggested change to all affected versions.

[jillian-maroket]

Suggested change

	To use standard RWX filesystem volumes, `migratable` must remain unset or be explicitly set to `false`.
	To use standard RWX filesystem volumes, the `migratable` parameter must be empty or explicitly set to `false`.

[glovecchi0]

Done, @jillian-maroket ! Thanks a lot for the review.

[Martin-Weiss]

Could you also change this:

kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
  name: longhorn-rwx
provisioner: driver.longhorn.io
allowVolumeExpansion: true
reclaimPolicy: Delete
volumeBindingMode: Immediate
parameters:
  numberOfReplicas: "3"
  staleReplicaTimeout: "2880"
  fromBackup: ""
  fsType: "ext4"
  nfsOptions: "vers=4.2,noresvport,softerr,timeo=600,retrans=5"

to this (adding migratable: false):

kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
  name: longhorn-rwx
provisioner: driver.longhorn.io
allowVolumeExpansion: true
reclaimPolicy: Delete
volumeBindingMode: Immediate
migratable: false
parameters:
  numberOfReplicas: "3"
  staleReplicaTimeout: "2880"
  fromBackup: ""
  fsType: "ext4"
  nfsOptions: "vers=4.2,noresvport,softerr,timeo=600,retrans=5"`

[glovecchi0]

Could you also change this:

kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
  name: longhorn-rwx
provisioner: driver.longhorn.io
allowVolumeExpansion: true
reclaimPolicy: Delete
volumeBindingMode: Immediate
parameters:
  numberOfReplicas: "3"
  staleReplicaTimeout: "2880"
  fromBackup: ""
  fsType: "ext4"
  nfsOptions: "vers=4.2,noresvport,softerr,timeo=600,retrans=5"

to this (adding migratable: false):

kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
  name: longhorn-rwx
provisioner: driver.longhorn.io
allowVolumeExpansion: true
reclaimPolicy: Delete
volumeBindingMode: Immediate
migratable: false
parameters:
  numberOfReplicas: "3"
  staleReplicaTimeout: "2880"
  fromBackup: ""
  fsType: "ext4"
  nfsOptions: "vers=4.2,noresvport,softerr,timeo=600,retrans=5"`

With the added disclosure, this change probably isn't necessary. Let's see what others say, too...

[jillian-maroket]

Thanks!

[jillian-maroket]

Could you also change this:

kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
  name: longhorn-rwx
provisioner: driver.longhorn.io
allowVolumeExpansion: true
reclaimPolicy: Delete
volumeBindingMode: Immediate
parameters:
  numberOfReplicas: "3"
  staleReplicaTimeout: "2880"
  fromBackup: ""
  fsType: "ext4"
  nfsOptions: "vers=4.2,noresvport,softerr,timeo=600,retrans=5"

to this (adding migratable: false):

kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
  name: longhorn-rwx
provisioner: driver.longhorn.io
allowVolumeExpansion: true
reclaimPolicy: Delete
volumeBindingMode: Immediate
migratable: false
parameters:
  numberOfReplicas: "3"
  staleReplicaTimeout: "2880"
  fromBackup: ""
  fsType: "ext4"
  nfsOptions: "vers=4.2,noresvport,softerr,timeo=600,retrans=5"`

With the added disclosure, this change probably isn't necessary. Let's see what others say, too...

Something like this could work:

migratable: false # Must be empty or set to `false` when using standard RWX filesystem volumes

[glovecchi0]

migratable: false # Must be empty or set to false when using standard RWX filesystem volumes

Done! Thanks again :)