secondary-storage 4.0 updates

add 4.0 content (sourced from https://mail-archive.com/qubes-users@googlegroups.com/msg14871.html)
add version headings
adjust R3.2 procedure for consistency with rest of document
remove "#" from R3.2 procedure because it works as regular user if permissions are set correctly
remove "known issues" heading so bullet points fall under R3.2 section instead of appearing to apply to both versions

configuration/secondary-storage.md

@@ -12,28 +12,67 @@ Storing AppVMs on Secondary Drives
 ==================================
 
 Suppose you have a fast but small primary SSD and a large but slow secondary
-HDD.  You want to store a subset of your AppVMs on the HDD. In dom0:
+HDD.  You want to store a subset of your AppVMs on the HDD.
 
-1. `# mv /var/lib/qubes/appvms/my-new-appvm
-/path/to/secondary/drive/my-new-appvm`
+### R4.0 ###
 
-2. `# ln -s /path/to/secondary/drive/my-new-appvm /var/lib/qubes/appvms/`
+Qubes 4.0 is more flexible than earlier versions about placing different VMs on
+different disks. For example, you can keep templates on one disk and
+AppVMs on another, without messy symlinks.
+
+Assuming you have already created a separate [volume group](https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html/logical_volume_manager_administration/vg_admin#VG_create) and
+[thin pool](https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html/logical_volume_manager_administration/thinly_provisioned_volume_creation)
+(not thin volume) for your HDD,
+first collect some information in a dom0 terminal:
+
+    sudo pvs
+    sudo lvs
+
+Take note of the VG and thin pool names for your HDD, then register it with Qubes:
+
+    # pool_name is a freely chosen pool name
+    # vg_name is LVM volume group name
+    # thin_pool_name is LVM thin pool name
+    qvm-pool --add pool_name lvm_thin -o volume_group=vg_name,thin_pool=thin_pool_name
+    
+Now, you can create qubes in that pool:
+
+    qvm-create -P pool_name --label red vmname
+
+It isn't possible to directly migrate an existing qube to the new pool, but
+you can clone it there, then remove the old one:
+
+    qvm-clone -P pool_name old_name new_name
+    qvm-remove old_name
+
+If that was a template, or other qube referenced elsewhere (NetVM or
+such), you will need to adjust those references manually after moving.
+For example:
+
+    qvm-prefs appvm_based_on_old_name_template template new_name
+
+In theory, you can still use file-based disk images ("file" pool driver),
+but it lacks some features such as you won't be able to do
+backups without shutting down the qube.
+
+### R3.2 ###
+
+In dom0:
+
+    mv /var/lib/qubes/appvms/my-new-appvm /path/to/secondary/drive/my-new-appvm
+    ln -s /path/to/secondary/drive/my-new-appvm /var/lib/qubes/appvms/
 
 Now, `my-new-appvm` will behave as if it were still stored on the primary SSD
 (except that it will probably be slower, since it's actually stored on the
 secondary HDD).
 
-Known Issues
-------------
-
  * The above procedure does **not** interfere with [Qubes Backup][]. However,
    attempting to symlink a `private.img` file (rather than the whole AppVM
    directory) is known to prevent the `private.img` file from being backed up.
    The same problem may occur if the above procedure is attempted on a
    [TemplateVM][]. [[1]]
 
- * This issue applies only to R3.1, not R3.2 or later:
-   After implementing the above procedure, starting `my-new-appvm` will cause
+ * After implementing the above procedure, starting `my-new-appvm` will cause
    dom0 notifications to occur stating that loop devices have been attached to
    dom0. This is normal. (No untrusted devices are actually being mounted to
    dom0.) Do not attempt to detach these disks. (They will automatically be