diff --git a/comfy/model_management.py b/comfy/model_management.py
index f4ed13899..f2e23c446 100644
--- a/comfy/model_management.py
+++ b/comfy/model_management.py
@@ -26,6 +26,14 @@ import importlib
 import platform
 import weakref
 import gc
+import os
+
+def get_mmap_mem_threshold_gb():
+    mmap_mem_threshold_gb = int(os.environ.get("MMAP_MEM_THRESHOLD_GB", "0"))
+    return mmap_mem_threshold_gb
+
+def get_free_disk():
+    return psutil.disk_usage("/").free
 
 class VRAMState(Enum):
     DISABLED = 0    #No vram present: no need to move models to vram
@@ -524,9 +532,7 @@ class LoadedModel:
         logging.debug(f"unpatch_weights: {unpatch_weights}")
         logging.debug(f"loaded_size: {self.model.loaded_size()/(1024*1024*1024)} GB")
         logging.debug(f"offload_device: {self.model.offload_device}")
-        available_memory = get_free_memory(self.model.offload_device)
-        logging.debug(f"before unload, available_memory of offload device {self.model.offload_device}: {available_memory/(1024*1024*1024)} GB")
-        # reserved_memory = 1024*1024*1024  # 1GB reserved memory for other usage
+
         # if available_memory < reserved_memory:
         #     logging.warning(f"Not enough cpu memory to unload. Available: {available_memory/(1024*1024*1024)} GB, Reserved: {reserved_memory/(1024*1024*1024)} GB")
         #     return False
@@ -537,30 +543,42 @@ class LoadedModel:
         #     memory_to_free = offload_memory
         #     logging.info(f"Not enough cpu memory to unload. Available: {available_memory/(1024*1024*1024)} GB, Reserved: {reserved_memory/(1024*1024*1024)} GB, Offload: {offload_memory/(1024*1024*1024)} GB")
         #     logging.info(f"Set memory_to_free to {memory_to_free/(1024*1024*1024)} GB")
-        try:
-            if memory_to_free is not None:
-                if memory_to_free < self.model.loaded_size():
-                    logging.debug("Do partially unload")
-                    freed = self.model.partially_unload(self.model.offload_device, memory_to_free)
-                    logging.debug(f"partially_unload freed vram: {freed/(1024*1024*1024)} GB")
-                    if freed >= memory_to_free:
-                        return False
+
+        if memory_to_free is None:
+            # free the full model
+            memory_to_free = self.model.loaded_size()
+
+        available_memory = get_free_memory(self.model.offload_device)
+        logging.debug(f"before unload, available_memory of offload device {self.model.offload_device}: {available_memory/(1024*1024*1024)} GB")
+
+        mmap_mem_threshold = get_mmap_mem_threshold_gb() * 1024 * 1024 * 1024  # this is reserved memory for other system usage
+        if memory_to_free > available_memory - mmap_mem_threshold or memory_to_free < self.model.loaded_size():
+            partially_unload = True
+        else:
+            partially_unload = False
+
+        if partially_unload:
+            logging.debug("Do partially unload")
+            freed = self.model.partially_unload(self.model.offload_device, memory_to_free)
+            logging.debug(f"partially_unload freed vram: {freed/(1024*1024*1024)} GB")
+            if freed < memory_to_free:
+                logging.warning(f"Partially unload not enough memory, freed {freed/(1024*1024*1024)} GB, memory_to_free {memory_to_free/(1024*1024*1024)} GB")
+        else:
             logging.debug("Do full unload")
             self.model.detach(unpatch_weights)
             logging.debug("Do full unload done")
-        except Exception as e:
-            logging.error(f"Error in model_unload: {e}")
-            available_memory = get_free_memory(self.model.offload_device)
-            logging.info(f"after error, available_memory of offload device {self.model.offload_device}: {available_memory/(1024*1024*1024)} GB")
-            return False
-        finally:
-            available_memory = get_free_memory(self.model.offload_device)
-            logging.debug(f"after unload, available_memory of offload device {self.model.offload_device}: {available_memory/(1024*1024*1024)} GB")
+            self.model_finalizer.detach()
+            self.model_finalizer = None
+            self.real_model = None
+
+        available_memory = get_free_memory(self.model.offload_device)
+        logging.debug(f"after unload, available_memory of offload device {self.model.offload_device}: {available_memory/(1024*1024*1024)} GB")
+
+        if partially_unload:
+            return False
+        else:
+            return True
 
-        self.model_finalizer.detach()
-        self.model_finalizer = None
-        self.real_model = None
-        return True
 
     def model_use_more_vram(self, extra_memory, force_patch_weights=False):
         return self.model.partially_load(self.device, extra_memory, force_patch_weights=force_patch_weights)
diff --git a/comfy/model_patcher.py b/comfy/model_patcher.py
index 115e401b3..361f15e5b 100644
--- a/comfy/model_patcher.py
+++ b/comfy/model_patcher.py
@@ -40,11 +40,11 @@ import comfy.patcher_extension
 import comfy.utils
 from comfy.comfy_types import UnetWrapperFunction
 from comfy.patcher_extension import CallbacksMP, PatcherInjection, WrappersMP
-from comfy.model_management import get_free_memory
+from comfy.model_management import get_free_memory, get_mmap_mem_threshold_gb, get_free_disk
 
 def need_mmap() -> bool:
     free_cpu_mem = get_free_memory(torch.device("cpu"))
-    mmap_mem_threshold_gb = int(os.environ.get("MMAP_MEM_THRESHOLD_GB", "0"))
+    mmap_mem_threshold_gb = get_mmap_mem_threshold_gb()
     if free_cpu_mem < mmap_mem_threshold_gb * 1024 * 1024 * 1024:
         logging.debug(f"Enabling mmap, current free cpu memory {free_cpu_mem/(1024*1024*1024)} GB < {mmap_mem_threshold_gb} GB")
         return True
@@ -972,6 +972,9 @@ class ModelPatcher:
                     if move_weight:
                         cast_weight = self.force_cast_weights
                         if need_mmap():
+                            if get_free_disk() < module_mem:
+                                logging.warning(f"Not enough disk space to offload {n} to mmap, current free disk space {get_free_disk()/(1024*1024*1024)} GB < {module_mem/(1024*1024*1024)} GB")
+                                break
                             # offload to mmap
                             model_to_mmap(m)
                         else: