diff --git a/scripts/update_payload/update_metadata_pb2.py b/scripts/update_payload/update_metadata_pb2.py
index 841cd22..ea4bc59 100644
--- a/scripts/update_payload/update_metadata_pb2.py
+++ b/scripts/update_payload/update_metadata_pb2.py
@@ -18,7 +18,7 @@
   package='chromeos_update_engine',
   syntax='proto2',
   serialized_options=b'H\003',
-  serialized_pb=b'\n\x15update_metadata.proto\x12\x16\x63hromeos_update_engine\"1\n\x06\x45xtent\x12\x13\n\x0bstart_block\x18\x01 \x01(\x04\x12\x12\n\nnum_blocks\x18\x02 \x01(\x04\"\x9f\x01\n\nSignatures\x12@\n\nsignatures\x18\x01 \x03(\x0b\x32,.chromeos_update_engine.Signatures.Signature\x1aO\n\tSignature\x12\x13\n\x07version\x18\x01 \x01(\rB\x02\x18\x01\x12\x0c\n\x04\x64\x61ta\x18\x02 \x01(\x0c\x12\x1f\n\x17unpadded_signature_size\x18\x03 \x01(\x07\"+\n\rPartitionInfo\x12\x0c\n\x04size\x18\x01 \x01(\x04\x12\x0c\n\x04hash\x18\x02 \x01(\x0c\"w\n\tImageInfo\x12\r\n\x05\x62oard\x18\x01 \x01(\t\x12\x0b\n\x03key\x18\x02 \x01(\t\x12\x0f\n\x07\x63hannel\x18\x03 \x01(\t\x12\x0f\n\x07version\x18\x04 \x01(\t\x12\x15\n\rbuild_channel\x18\x05 \x01(\t\x12\x15\n\rbuild_version\x18\x06 \x01(\t\"\xee\x03\n\x10InstallOperation\x12;\n\x04type\x18\x01 \x02(\x0e\x32-.chromeos_update_engine.InstallOperation.Type\x12\x13\n\x0b\x64\x61ta_offset\x18\x02 \x01(\x04\x12\x13\n\x0b\x64\x61ta_length\x18\x03 \x01(\x04\x12\x33\n\x0bsrc_extents\x18\x04 \x03(\x0b\x32\x1e.chromeos_update_engine.Extent\x12\x12\n\nsrc_length\x18\x05 \x01(\x04\x12\x33\n\x0b\x64st_extents\x18\x06 \x03(\x0b\x32\x1e.chromeos_update_engine.Extent\x12\x12\n\ndst_length\x18\x07 \x01(\x04\x12\x18\n\x10\x64\x61ta_sha256_hash\x18\x08 \x01(\x0c\x12\x17\n\x0fsrc_sha256_hash\x18\t \x01(\x0c\"\xad\x01\n\x04Type\x12\x0b\n\x07REPLACE\x10\x00\x12\x0e\n\nREPLACE_BZ\x10\x01\x12\x0c\n\x04MOVE\x10\x02\x1a\x02\x08\x01\x12\x0e\n\x06\x42SDIFF\x10\x03\x1a\x02\x08\x01\x12\x0f\n\x0bSOURCE_COPY\x10\x04\x12\x11\n\rSOURCE_BSDIFF\x10\x05\x12\x0e\n\nREPLACE_XZ\x10\x08\x12\x08\n\x04ZERO\x10\x06\x12\x0b\n\x07\x44ISCARD\x10\x07\x12\x11\n\rBROTLI_BSDIFF\x10\n\x12\x0c\n\x08PUFFDIFF\x10\t\"\xe8\x05\n\x0fPartitionUpdate\x12\x16\n\x0epartition_name\x18\x01 \x02(\t\x12\x17\n\x0frun_postinstall\x18\x02 \x01(\x08\x12\x18\n\x10postinstall_path\x18\x03 \x01(\t\x12\x17\n\x0f\x66ilesystem_type\x18\x04 \x01(\t\x12M\n\x17new_partition_signature\x18\x05 \x03(\x0b\x32,.chromeos_update_engine.Signatures.Signature\x12\x41\n\x12old_partition_info\x18\x06 \x01(\x0b\x32%.chromeos_update_engine.PartitionInfo\x12\x41\n\x12new_partition_info\x18\x07 \x01(\x0b\x32%.chromeos_update_engine.PartitionInfo\x12<\n\noperations\x18\x08 \x03(\x0b\x32(.chromeos_update_engine.InstallOperation\x12\x1c\n\x14postinstall_optional\x18\t \x01(\x08\x12=\n\x15hash_tree_data_extent\x18\n \x01(\x0b\x32\x1e.chromeos_update_engine.Extent\x12\x38\n\x10hash_tree_extent\x18\x0b \x01(\x0b\x32\x1e.chromeos_update_engine.Extent\x12\x1b\n\x13hash_tree_algorithm\x18\x0c \x01(\t\x12\x16\n\x0ehash_tree_salt\x18\r \x01(\x0c\x12\x37\n\x0f\x66\x65\x63_data_extent\x18\x0e \x01(\x0b\x32\x1e.chromeos_update_engine.Extent\x12\x32\n\nfec_extent\x18\x0f \x01(\x0b\x32\x1e.chromeos_update_engine.Extent\x12\x14\n\tfec_roots\x18\x10 \x01(\r:\x01\x32\x12\x0f\n\x07version\x18\x11 \x01(\t\"L\n\x15\x44ynamicPartitionGroup\x12\x0c\n\x04name\x18\x01 \x02(\t\x12\x0c\n\x04size\x18\x02 \x01(\x04\x12\x17\n\x0fpartition_names\x18\x03 \x03(\t\"s\n\x18\x44ynamicPartitionMetadata\x12=\n\x06groups\x18\x01 \x03(\x0b\x32-.chromeos_update_engine.DynamicPartitionGroup\x12\x18\n\x10snapshot_enabled\x18\x02 \x01(\x08\"\xe1\x06\n\x14\x44\x65ltaArchiveManifest\x12H\n\x12install_operations\x18\x01 \x03(\x0b\x32(.chromeos_update_engine.InstallOperationB\x02\x18\x01\x12O\n\x19kernel_install_operations\x18\x02 \x03(\x0b\x32(.chromeos_update_engine.InstallOperationB\x02\x18\x01\x12\x18\n\nblock_size\x18\x03 \x01(\r:\x04\x34\x30\x39\x36\x12\x19\n\x11signatures_offset\x18\x04 \x01(\x04\x12\x17\n\x0fsignatures_size\x18\x05 \x01(\x04\x12\x42\n\x0fold_kernel_info\x18\x06 \x01(\x0b\x32%.chromeos_update_engine.PartitionInfoB\x02\x18\x01\x12\x42\n\x0fnew_kernel_info\x18\x07 \x01(\x0b\x32%.chromeos_update_engine.PartitionInfoB\x02\x18\x01\x12\x42\n\x0fold_rootfs_info\x18\x08 \x01(\x0b\x32%.chromeos_update_engine.PartitionInfoB\x02\x18\x01\x12\x42\n\x0fnew_rootfs_info\x18\t \x01(\x0b\x32%.chromeos_update_engine.PartitionInfoB\x02\x18\x01\x12\x39\n\x0eold_image_info\x18\n \x01(\x0b\x32!.chromeos_update_engine.ImageInfo\x12\x39\n\x0enew_image_info\x18\x0b \x01(\x0b\x32!.chromeos_update_engine.ImageInfo\x12\x18\n\rminor_version\x18\x0c \x01(\r:\x01\x30\x12;\n\npartitions\x18\r \x03(\x0b\x32\'.chromeos_update_engine.PartitionUpdate\x12\x15\n\rmax_timestamp\x18\x0e \x01(\x03\x12T\n\x1a\x64ynamic_partition_metadata\x18\x0f \x01(\x0b\x32\x30.chromeos_update_engine.DynamicPartitionMetadata\x12\x16\n\x0epartial_update\x18\x10 \x01(\x08\x42\x02H\x03'
+  serialized_pb=b'\n\x15update_metadata.proto\x12\x16\x63hromeos_update_engine\"1\n\x06\x45xtent\x12\x13\n\x0bstart_block\x18\x01 \x01(\x04\x12\x12\n\nnum_blocks\x18\x02 \x01(\x04\"\x9f\x01\n\nSignatures\x12@\n\nsignatures\x18\x01 \x03(\x0b\x32,.chromeos_update_engine.Signatures.Signature\x1aO\n\tSignature\x12\x13\n\x07version\x18\x01 \x01(\rB\x02\x18\x01\x12\x0c\n\x04\x64\x61ta\x18\x02 \x01(\x0c\x12\x1f\n\x17unpadded_signature_size\x18\x03 \x01(\x07\"+\n\rPartitionInfo\x12\x0c\n\x04size\x18\x01 \x01(\x04\x12\x0c\n\x04hash\x18\x02 \x01(\x0c\"w\n\tImageInfo\x12\r\n\x05\x62oard\x18\x01 \x01(\t\x12\x0b\n\x03key\x18\x02 \x01(\t\x12\x0f\n\x07\x63hannel\x18\x03 \x01(\t\x12\x0f\n\x07version\x18\x04 \x01(\t\x12\x15\n\rbuild_channel\x18\x05 \x01(\t\x12\x15\n\rbuild_version\x18\x06 \x01(\t\"\xee\x03\n\x10InstallOperation\x12;\n\x04type\x18\x01 \x02(\x0e\x32-.chromeos_update_engine.InstallOperation.Type\x12\x13\n\x0b\x64\x61ta_offset\x18\x02 \x01(\x04\x12\x13\n\x0b\x64\x61ta_length\x18\x03 \x01(\x04\x12\x33\n\x0bsrc_extents\x18\x04 \x03(\x0b\x32\x1e.chromeos_update_engine.Extent\x12\x12\n\nsrc_length\x18\x05 \x01(\x04\x12\x33\n\x0b\x64st_extents\x18\x06 \x03(\x0b\x32\x1e.chromeos_update_engine.Extent\x12\x12\n\ndst_length\x18\x07 \x01(\x04\x12\x18\n\x10\x64\x61ta_sha256_hash\x18\x08 \x01(\x0c\x12\x17\n\x0fsrc_sha256_hash\x18\t \x01(\x0c\"\xad\x01\n\x04Type\x12\x0b\n\x07REPLACE\x10\x00\x12\x0e\n\nREPLACE_BZ\x10\x01\x12\x0c\n\x04MOVE\x10\x02\x1a\x02\x08\x01\x12\x0e\n\x06\x42SDIFF\x10\x03\x1a\x02\x08\x01\x12\x0f\n\x0bSOURCE_COPY\x10\x04\x12\x11\n\rSOURCE_BSDIFF\x10\x05\x12\x0e\n\nREPLACE_XZ\x10\x08\x12\x08\n\x04ZERO\x10\x06\x12\x0b\n\x07\x44ISCARD\x10\x07\x12\x11\n\rBROTLI_BSDIFF\x10\n\x12\x0c\n\x08PUFFDIFF\x10\t\"\xcf\x01\n\x11\x43owMergeOperation\x12<\n\x04type\x18\x01 \x01(\x0e\x32..chromeos_update_engine.CowMergeOperation.Type\x12\x32\n\nsrc_extent\x18\x02 \x01(\x0b\x32\x1e.chromeos_update_engine.Extent\x12\x32\n\ndst_extent\x18\x03 \x01(\x0b\x32\x1e.chromeos_update_engine.Extent\"\x14\n\x04Type\x12\x0c\n\x08\x43OW_COPY\x10\x00\"\xc8\x06\n\x0fPartitionUpdate\x12\x16\n\x0epartition_name\x18\x01 \x02(\t\x12\x17\n\x0frun_postinstall\x18\x02 \x01(\x08\x12\x18\n\x10postinstall_path\x18\x03 \x01(\t\x12\x17\n\x0f\x66ilesystem_type\x18\x04 \x01(\t\x12M\n\x17new_partition_signature\x18\x05 \x03(\x0b\x32,.chromeos_update_engine.Signatures.Signature\x12\x41\n\x12old_partition_info\x18\x06 \x01(\x0b\x32%.chromeos_update_engine.PartitionInfo\x12\x41\n\x12new_partition_info\x18\x07 \x01(\x0b\x32%.chromeos_update_engine.PartitionInfo\x12<\n\noperations\x18\x08 \x03(\x0b\x32(.chromeos_update_engine.InstallOperation\x12\x1c\n\x14postinstall_optional\x18\t \x01(\x08\x12=\n\x15hash_tree_data_extent\x18\n \x01(\x0b\x32\x1e.chromeos_update_engine.Extent\x12\x38\n\x10hash_tree_extent\x18\x0b \x01(\x0b\x32\x1e.chromeos_update_engine.Extent\x12\x1b\n\x13hash_tree_algorithm\x18\x0c \x01(\t\x12\x16\n\x0ehash_tree_salt\x18\r \x01(\x0c\x12\x37\n\x0f\x66\x65\x63_data_extent\x18\x0e \x01(\x0b\x32\x1e.chromeos_update_engine.Extent\x12\x32\n\nfec_extent\x18\x0f \x01(\x0b\x32\x1e.chromeos_update_engine.Extent\x12\x14\n\tfec_roots\x18\x10 \x01(\r:\x01\x32\x12\x0f\n\x07version\x18\x11 \x01(\t\x12\x43\n\x10merge_operations\x18\x12 \x03(\x0b\x32).chromeos_update_engine.CowMergeOperation\x12\x19\n\x11\x65stimate_cow_size\x18\x13 \x01(\x04\"L\n\x15\x44ynamicPartitionGroup\x12\x0c\n\x04name\x18\x01 \x02(\t\x12\x0c\n\x04size\x18\x02 \x01(\x04\x12\x17\n\x0fpartition_names\x18\x03 \x03(\t\"s\n\x18\x44ynamicPartitionMetadata\x12=\n\x06groups\x18\x01 \x03(\x0b\x32-.chromeos_update_engine.DynamicPartitionGroup\x12\x18\n\x10snapshot_enabled\x18\x02 \x01(\x08\"\xe1\x06\n\x14\x44\x65ltaArchiveManifest\x12H\n\x12install_operations\x18\x01 \x03(\x0b\x32(.chromeos_update_engine.InstallOperationB\x02\x18\x01\x12O\n\x19kernel_install_operations\x18\x02 \x03(\x0b\x32(.chromeos_update_engine.InstallOperationB\x02\x18\x01\x12\x18\n\nblock_size\x18\x03 \x01(\r:\x04\x34\x30\x39\x36\x12\x19\n\x11signatures_offset\x18\x04 \x01(\x04\x12\x17\n\x0fsignatures_size\x18\x05 \x01(\x04\x12\x42\n\x0fold_kernel_info\x18\x06 \x01(\x0b\x32%.chromeos_update_engine.PartitionInfoB\x02\x18\x01\x12\x42\n\x0fnew_kernel_info\x18\x07 \x01(\x0b\x32%.chromeos_update_engine.PartitionInfoB\x02\x18\x01\x12\x42\n\x0fold_rootfs_info\x18\x08 \x01(\x0b\x32%.chromeos_update_engine.PartitionInfoB\x02\x18\x01\x12\x42\n\x0fnew_rootfs_info\x18\t \x01(\x0b\x32%.chromeos_update_engine.PartitionInfoB\x02\x18\x01\x12\x39\n\x0eold_image_info\x18\n \x01(\x0b\x32!.chromeos_update_engine.ImageInfo\x12\x39\n\x0enew_image_info\x18\x0b \x01(\x0b\x32!.chromeos_update_engine.ImageInfo\x12\x18\n\rminor_version\x18\x0c \x01(\r:\x01\x30\x12;\n\npartitions\x18\r \x03(\x0b\x32\'.chromeos_update_engine.PartitionUpdate\x12\x15\n\rmax_timestamp\x18\x0e \x01(\x03\x12T\n\x1a\x64ynamic_partition_metadata\x18\x0f \x01(\x0b\x32\x30.chromeos_update_engine.DynamicPartitionMetadata\x12\x16\n\x0epartial_update\x18\x10 \x01(\x08\x42\x02H\x03'
 )
 
 
@@ -81,6 +81,24 @@
 )
 _sym_db.RegisterEnumDescriptor(_INSTALLOPERATION_TYPE)
 
+_COWMERGEOPERATION_TYPE = _descriptor.EnumDescriptor(
+  name='Type',
+  full_name='chromeos_update_engine.CowMergeOperation.Type',
+  filename=None,
+  file=DESCRIPTOR,
+  values=[
+    _descriptor.EnumValueDescriptor(
+      name='COW_COPY', index=0, number=0,
+      serialized_options=None,
+      type=None),
+  ],
+  containing_type=None,
+  serialized_options=None,
+  serialized_start=1113,
+  serialized_end=1133,
+)
+_sym_db.RegisterEnumDescriptor(_COWMERGEOPERATION_TYPE)
+
 
 _EXTENT = _descriptor.Descriptor(
   name='Extent',
@@ -387,6 +405,52 @@
 )
 
 
+_COWMERGEOPERATION = _descriptor.Descriptor(
+  name='CowMergeOperation',
+  full_name='chromeos_update_engine.CowMergeOperation',
+  filename=None,
+  file=DESCRIPTOR,
+  containing_type=None,
+  fields=[
+    _descriptor.FieldDescriptor(
+      name='type', full_name='chromeos_update_engine.CowMergeOperation.type', index=0,
+      number=1, type=14, cpp_type=8, label=1,
+      has_default_value=False, default_value=0,
+      message_type=None, enum_type=None, containing_type=None,
+      is_extension=False, extension_scope=None,
+      serialized_options=None, file=DESCRIPTOR),
+    _descriptor.FieldDescriptor(
+      name='src_extent', full_name='chromeos_update_engine.CowMergeOperation.src_extent', index=1,
+      number=2, type=11, cpp_type=10, label=1,
+      has_default_value=False, default_value=None,
+      message_type=None, enum_type=None, containing_type=None,
+      is_extension=False, extension_scope=None,
+      serialized_options=None, file=DESCRIPTOR),
+    _descriptor.FieldDescriptor(
+      name='dst_extent', full_name='chromeos_update_engine.CowMergeOperation.dst_extent', index=2,
+      number=3, type=11, cpp_type=10, label=1,
+      has_default_value=False, default_value=None,
+      message_type=None, enum_type=None, containing_type=None,
+      is_extension=False, extension_scope=None,
+      serialized_options=None, file=DESCRIPTOR),
+  ],
+  extensions=[
+  ],
+  nested_types=[],
+  enum_types=[
+    _COWMERGEOPERATION_TYPE,
+  ],
+  serialized_options=None,
+  is_extendable=False,
+  syntax='proto2',
+  extension_ranges=[],
+  oneofs=[
+  ],
+  serialized_start=926,
+  serialized_end=1133,
+)
+
+
 _PARTITIONUPDATE = _descriptor.Descriptor(
   name='PartitionUpdate',
   full_name='chromeos_update_engine.PartitionUpdate',
@@ -513,6 +577,20 @@
       message_type=None, enum_type=None, containing_type=None,
       is_extension=False, extension_scope=None,
       serialized_options=None, file=DESCRIPTOR),
+    _descriptor.FieldDescriptor(
+      name='merge_operations', full_name='chromeos_update_engine.PartitionUpdate.merge_operations', index=17,
+      number=18, type=11, cpp_type=10, label=3,
+      has_default_value=False, default_value=[],
+      message_type=None, enum_type=None, containing_type=None,
+      is_extension=False, extension_scope=None,
+      serialized_options=None, file=DESCRIPTOR),
+    _descriptor.FieldDescriptor(
+      name='estimate_cow_size', full_name='chromeos_update_engine.PartitionUpdate.estimate_cow_size', index=18,
+      number=19, type=4, cpp_type=4, label=1,
+      has_default_value=False, default_value=0,
+      message_type=None, enum_type=None, containing_type=None,
+      is_extension=False, extension_scope=None,
+      serialized_options=None, file=DESCRIPTOR),
   ],
   extensions=[
   ],
@@ -525,8 +603,8 @@
   extension_ranges=[],
   oneofs=[
   ],
-  serialized_start=926,
-  serialized_end=1670,
+  serialized_start=1136,
+  serialized_end=1976,
 )
 
 
@@ -570,8 +648,8 @@
   extension_ranges=[],
   oneofs=[
   ],
-  serialized_start=1672,
-  serialized_end=1748,
+  serialized_start=1978,
+  serialized_end=2054,
 )
 
 
@@ -608,8 +686,8 @@
   extension_ranges=[],
   oneofs=[
   ],
-  serialized_start=1750,
-  serialized_end=1865,
+  serialized_start=2056,
+  serialized_end=2171,
 )
 
 
@@ -744,8 +822,8 @@
   extension_ranges=[],
   oneofs=[
   ],
-  serialized_start=1868,
-  serialized_end=2733,
+  serialized_start=2174,
+  serialized_end=3039,
 )
 
 _SIGNATURES_SIGNATURE.containing_type = _SIGNATURES
@@ -754,6 +832,10 @@
 _INSTALLOPERATION.fields_by_name['src_extents'].message_type = _EXTENT
 _INSTALLOPERATION.fields_by_name['dst_extents'].message_type = _EXTENT
 _INSTALLOPERATION_TYPE.containing_type = _INSTALLOPERATION
+_COWMERGEOPERATION.fields_by_name['type'].enum_type = _COWMERGEOPERATION_TYPE
+_COWMERGEOPERATION.fields_by_name['src_extent'].message_type = _EXTENT
+_COWMERGEOPERATION.fields_by_name['dst_extent'].message_type = _EXTENT
+_COWMERGEOPERATION_TYPE.containing_type = _COWMERGEOPERATION
 _PARTITIONUPDATE.fields_by_name['new_partition_signature'].message_type = _SIGNATURES_SIGNATURE
 _PARTITIONUPDATE.fields_by_name['old_partition_info'].message_type = _PARTITIONINFO
 _PARTITIONUPDATE.fields_by_name['new_partition_info'].message_type = _PARTITIONINFO
@@ -762,6 +844,7 @@
 _PARTITIONUPDATE.fields_by_name['hash_tree_extent'].message_type = _EXTENT
 _PARTITIONUPDATE.fields_by_name['fec_data_extent'].message_type = _EXTENT
 _PARTITIONUPDATE.fields_by_name['fec_extent'].message_type = _EXTENT
+_PARTITIONUPDATE.fields_by_name['merge_operations'].message_type = _COWMERGEOPERATION
 _DYNAMICPARTITIONMETADATA.fields_by_name['groups'].message_type = _DYNAMICPARTITIONGROUP
 _DELTAARCHIVEMANIFEST.fields_by_name['install_operations'].message_type = _INSTALLOPERATION
 _DELTAARCHIVEMANIFEST.fields_by_name['kernel_install_operations'].message_type = _INSTALLOPERATION
@@ -778,6 +861,7 @@
 DESCRIPTOR.message_types_by_name['PartitionInfo'] = _PARTITIONINFO
 DESCRIPTOR.message_types_by_name['ImageInfo'] = _IMAGEINFO
 DESCRIPTOR.message_types_by_name['InstallOperation'] = _INSTALLOPERATION
+DESCRIPTOR.message_types_by_name['CowMergeOperation'] = _COWMERGEOPERATION
 DESCRIPTOR.message_types_by_name['PartitionUpdate'] = _PARTITIONUPDATE
 DESCRIPTOR.message_types_by_name['DynamicPartitionGroup'] = _DYNAMICPARTITIONGROUP
 DESCRIPTOR.message_types_by_name['DynamicPartitionMetadata'] = _DYNAMICPARTITIONMETADATA
@@ -827,6 +911,13 @@
   })
 _sym_db.RegisterMessage(InstallOperation)
 
+CowMergeOperation = _reflection.GeneratedProtocolMessageType('CowMergeOperation', (_message.Message,), {
+  'DESCRIPTOR' : _COWMERGEOPERATION,
+  '__module__' : 'update_metadata_pb2'
+  # @@protoc_insertion_point(class_scope:chromeos_update_engine.CowMergeOperation)
+  })
+_sym_db.RegisterMessage(CowMergeOperation)
+
 PartitionUpdate = _reflection.GeneratedProtocolMessageType('PartitionUpdate', (_message.Message,), {
   'DESCRIPTOR' : _PARTITIONUPDATE,
   '__module__' : 'update_metadata_pb2'
diff --git a/update_metadata.proto b/update_metadata.proto
index 373ee5e..ca59a02 100644
--- a/update_metadata.proto
+++ b/update_metadata.proto
@@ -314,6 +314,11 @@
   // skip writing the raw bytes for these extents. During snapshot merge, the
   // bytes will read from the source partitions instead.
   repeated CowMergeOperation merge_operations = 18;
+
+  // Estimated size for COW image. This is used by libsnapshot
+  // as a hint. If set to 0, libsnapshot should use alternative
+  // methods for estimating size.
+  optional uint64 estimate_cow_size = 19;
 }
 
 message DynamicPartitionGroup {