use alignment_data() in PartitionStretchy

also add alignment_data() to Raid

subiquity/models/filesystem.py

@@ -758,6 +758,10 @@ class Raid(_Device):
                     return s
         return get_raid_size(self.raidlevel, self.devices)
 
+    def alignment_data(self):
+        ptable = self.ptable_for_new_partition()
+        return self._m._partition_alignment_data[ptable]
+
     @property
     def available_for_partitions(self):
         # For some reason, the overhead on RAID devices seems to be

subiquity/ui/views/filesystem/partition.py

@@ -57,9 +57,6 @@ from subiquity.ui.mount import (
 log = logging.getLogger('subiquity.ui.views.filesystem.partition')
 
 
-DEFAULT_ALIGNMENT = 1 << 20
-
-
 class FSTypeField(FormField):
 
     takes_default_style = False
@@ -383,7 +380,7 @@ class PartitionStretchy(Stretchy):
             alignment = LVM_CHUNK_SIZE
             lvm_names = {p.name for p in disk.partitions()}
         else:
-            alignment = DEFAULT_ALIGNMENT
+            alignment = disk.alignment_data().part_align
             lvm_names = None
         if self.partition:
             if partition.flag in ["bios_grub", "prep"]:
@@ -576,7 +573,8 @@ class FormatEntireStretchy(Stretchy):
         elif not isinstance(device, Disk):
             initial['fstype'] = 'ext4'
         self.form = PartitionForm(
-            self.model, 0, initial, None, device, DEFAULT_ALIGNMENT)
+            self.model, 0, initial, None, device,
+            alignment=device.alignment_data().part_align)
         self.form.remove_field('size')
         self.form.remove_field('name')