reduce error to local backends only

helpers/data_backend/factory.py

@@ -1054,7 +1054,9 @@ def configure_multi_databackend(args: dict, accelerator, text_encoders, tokenize
                     f"VAE image embed cache directory {backend.get('cache_dir_vae')} is the same as the text embed cache directory. This is not allowed, the trainer will get confused."
                 )
 
-            if vae_cache_dir is None or vae_cache_dir == "":
+            if backend["type"] == "local" and (
+                vae_cache_dir is None or vae_cache_dir == ""
+            ):
                 raise ValueError(
                     f"VAE image embed cache directory {backend.get('cache_dir_vae')} is not set. This is required for the VAE image embed cache."
                 )