ceph: add a directory layout for secondary ec data pool

when creating ec fs, create replicated pool as primary
pool and ec pool as secondary pool, creating ec pool
as primary is not encouraged and it will lead to failure.

Closes: #8210
Signed-off-by: subhamkrai <srai@redhat.com>

Documentation/ceph-filesystem-crd.md

@@ -86,6 +86,8 @@ spec:
     replicated:
       size: 3
   dataPools:
+    - replicated:
+        size: 3
     - erasureCoded:
         dataChunks: 2
         codingChunks: 1
@@ -94,8 +96,7 @@ spec:
     activeStandby: true
 ```
 
-(These definitions can also be found in the [`filesystem-ec.yaml`](https://github.com/rook/rook/blob/{{ branchName }}/cluster/examples/kubernetes/ceph/filesystem-ec.yaml) file.
-Also see an example in the [`storageclass-ec.yaml`](https://github.com/rook/rook/blob/{{ branchName }}/cluster/examples/kubernetes/ceph/csi/cephfs/storageclass-ec.yaml) for how to configure the volume.)
+**IMPORTANT**: For erasure coded pools, we have to create a replicated pool as the default data pool and an erasure-coded pool as a secondary pool.
 
 ### Mirroring