PowerScale: Create a cascaded replication properly on OneFS

The main idea to keep in mind while configuring a cascaded replication. Ensure that replication job A_B should finish with "success/needs_attention" before starting replication job B_C.

Always, we should avoid that replication job A_B status is "failed OR canceled OR running OR paused" while replication job B_C starts.

In order to reach the above conditions:

1. We can make the replication policy from A_B to create a target snapshot with the name pattern "Archive-%{SrcCluster}-%{PolicyName}-%Y-%m-%d_%H-%M-%S" when the job is finished with success.

Cluster_A# isi sync policies create --name=A_B --source-root-path=/ifs/folder_A --target-host=xxx.xxx.xxx.xxx --target-path=/ifs/folder_B --action=sync --target-snapshot-archive=yes --target-snapshot-pattern=Archive-%{SrcCluster}-%{PolicyName}-%Y-%m-%d_%H-%M-%S --target-snapshot-expiration=5D

--target-snapshot-pattern=Archive-%{SrcCluster}-%

2. Then we make the replication policy from B_C to start only when a source snapshot pattern "Archive-*" is created.
   
   Cluster_B# isi sync policies create --name=B_C --source-root-path=/ifs/folder_B --target-host=xxx.xxx.xxx.xxx --target-path=/ifs/folder_C --action=sync --schedule=when-snapshot-taken --snapshot-sync-pattern="Archive-*" --snapshot-sync-existing=yes
   
   
   This will guarantee that the B_C replication job starts only after A_B replication job completes with success + the B_C schedule is tied to the A_B schedule.
   
   Check below from LAB:
   
   Cluster_A# cd /ifs/folder_A
Cluster_A# ls -lh
total 10249
-rw-r--r--    1 root  wheel    10M Jul 14 20:51 file
Cluster_A# isi sync jobs start A_B
Cluster_A# isi sync reports list
Policy Name  Job ID  Start Time          End Time            Action  State
-----------------------------------------------------------------------------
A_B          1       2021-07-14T20:51:22 2021-07-14T20:51:31 run     finished
-----------------------------------------------------------------------------
Total: 1

Cluster_B# cd /ifs/folder_B
Cluster_B# ls -lh
total 10249
-rw-r--r--    1 root  wheel    10M Jul 14 20:51 file
Cluster_B# isi sync reports list
Policy Name  Job ID  Start Time          End Time            Action  State
-----------------------------------------------------------------------------
B_C          2       2021-07-14T20:51:51 2021-07-14T20:52:10 run     finished
B_C          1       2021-07-14T20:51:32 2021-07-14T20:51:38 run     finished
-----------------------------------------------------------------------------
Total: 2

Cluster_C# cd /ifs/folder_C
Cluster_C# ls -lh
total 10249
-rw-r--r--     1 root  wheel    10M Jul 14 20:51 file