Add MeG migration instructions

pages/meg/99-support/migration-to-merlin7.md

@@ -45,16 +45,16 @@ A `experiment_migration.setup` migration script must be executed from **any MeG
 
 #### When using the local `root` account
 - The script **must be executed after every reboot** of the destination nodes.
-- **Reason:** On Merlin7, the home directory for the `root` user resides on ephemeral storage (no physical disk).  
+- **Reason:** On Merlin7, the home directory for the `root` user resides on ephemeral storage (no physical disk).
 After a reboot, this directory is cleaned, so **SSH keys need to be redeployed** before running the migration again.
 
 #### When using a PSI Active Directory (AD) account
-- Applicable accounts include, for example:  
-  - `gac-meg2_data`  
+- Applicable accounts include, for example:
+  - `gac-meg2_data`
   - `gac-meg2`
 - The script only needs to be executed **once**, provided that:
   - The home directory for the AD account is located on a shared storage area.
-  - This shared storage is accessible from the node executing the transfer.  
+  - This shared storage is accessible from the node executing the transfer.
 - **Reason:** On Merlin7, these accounts have their home directories on persistent shared storage, so the SSH keys remain available across reboots.
 
 To run it:
@@ -76,7 +76,7 @@ If you are stuck, email: [merlin-admins@lists.psi.ch](mailto:merlin-admins@lists
 
 ### Migration Procedure
 
-1. **Run an initial sync**
+1. **Run an initial sync**, ideally within a `tmux` session
    * This copies the bulk of the data from MeG to Merlin7.
    * **IMPORTANT: Do not modify the destination directories**
    * Please, before starting the transfer ensure that:
@@ -142,9 +142,16 @@ Options:
 
 > Defaults can be updated if necessary.
 
-#### Migration example
+#### Migration examples
 
-The following example migrates the entire online data
+##### Example: Migrating the Entire `online` Directory
+
+The following example demonstrates how to migrate the **entire `online`** directory.
+
+{{site.data.alerts.tip}}
+You may also choose to migrate only specific subdirectories if needed.
+However, migrating full directories is generally <b>simpler</b> and <b>less error-prone</b> compared to handling multiple subdirectory migrations.
+{{site.data.alerts.end}}
 
 ```bash
 [root@meg-s-001 bin]# experiment_migration.bash -b /meg -S /data/project/meg -S data1 -D data1 -p "online"                                                                                                                                                 
@@ -158,7 +165,13 @@ Please confirm to start (y/N): N
 ❌ Transfer cancelled by user.
 ```
 
-The following example migrates a subdirectory:
+##### Example: Migrating a Specific Subdirectory
+
+The following example demonstrates how to migrate **only a subdirectory**.
+
+⚠️ **Important:**  
+- When migrating a subdirectory, **do not** run concurrent migrations on its parent directories.
+- For example, avoid running migrations with `-p "shared"` while simultaneously migrating `-p "shared/subprojects"`.
 
 ```bash
 [root@meg-s-001 bin]# experiment_migration.bash -b /meg -B /data/project/meg -S data1 -D data1 -p "shared/subprojects/meg1"
@@ -170,3 +183,5 @@ The following example migrates a subdirectory:
 
 Please confirm to start (y/N): N
 ```
+
+This command initiates the migration of the directory: `/meg/data1/shared/subprojects/meg1` →  `login002.merlin7.psi.ch:/data/project/meg/data1/shared/subprojects/meg1`