diff --git a/answerfile.py b/answerfile.py
index 441befd4..26b46a5d 100644
--- a/answerfile.py
+++ b/answerfile.py
@@ -347,7 +347,7 @@ def parseDisks(self):
         if SR_TYPE_LARGE_BLOCK and len(large_block_disks) > 0:
             default_sr_type = SR_TYPE_LARGE_BLOCK
         else:
-            default_sr_type = SR_TYPE_LVM
+            default_sr_type = SR_TYPE_EXT
 
         sr_type = getMapAttribute(self.top_node,
                                   ['sr-type', 'srtype'],
diff --git a/doc/answerfile.txt b/doc/answerfile.txt
index e0e1fd7b..41fed16d 100644
--- a/doc/answerfile.txt
+++ b/doc/answerfile.txt
@@ -318,10 +318,14 @@ Format of 'source' and 'driver-source'
 
     Local SR type.
 
-    Default: lvm if the disks included in local SR storage all have 512 byte
+    Default: ext if the disks included in local SR storage all have 512 byte
              logical blocks, otherwise (when available) the SR type from
              the large-block-capable-sr-type feature
 
+    Note that while it reflects the default choice in the text UI,
+    this differs from XenServer and from XCP-ng releases lower than
+    8.3, where the default was "lvm".
+
 
 Upgrade Elements
 ----------------
diff --git a/tui/installer/screens.py b/tui/installer/screens.py
index aa09d6e7..33149cc8 100644
--- a/tui/installer/screens.py
+++ b/tui/installer/screens.py
@@ -830,13 +830,14 @@ def get_sr_type(answers):
                                    for disk in guest_disks)
 
     if not need_large_block_sr_type or not constants.SR_TYPE_LARGE_BLOCK:
-        srtype = answers.get('sr-type', constants.SR_TYPE_LVM)
-        txt = "Enable thin provisioning"
-        if len(BRAND_VDI) > 0:
-            txt += " (Optimized storage for %s)" % BRAND_VDI
-        tb = Checkbox(txt, srtype == constants.SR_TYPE_EXT and 1 or 0)
-        content = tb
-        get_type = lambda: tb.selected() and constants.SR_TYPE_EXT or constants.SR_TYPE_LVM
+        srtype = answers.get('sr-type', constants.SR_TYPE_EXT)
+        rb = RadioBar(tui.screen, (("EXT: file based. Thin provisioning.",
+                                    constants.SR_TYPE_EXT, srtype == constants.SR_TYPE_EXT),
+                                   ("LVM: block based. Thick provisioning.",
+                                    constants.SR_TYPE_LVM, srtype == constants.SR_TYPE_LVM),
+                                   ))
+        content = rb
+        get_type = lambda: rb.getSelection()
         buttons = ButtonBar(tui.screen, [('Ok', 'ok'), ('Back', 'back')])
     else:
         content = TextboxReflowed(40,