diff --git a/s3fs/core.py b/s3fs/core.py
index 43acd603..6f8d071a 100644
--- a/s3fs/core.py
+++ b/s3fs/core.py
@@ -273,7 +273,7 @@ class S3FileSystem(AsyncFileSystem):
     connect_timeout = 5
     retries = 5
     read_timeout = 15
-    default_block_size = 5 * 2**20
+    default_block_size = 50 * 2**20
     protocol = ("s3", "s3a")
     _extra_tokenize_attributes = ("default_block_size",)
 
@@ -299,7 +299,7 @@ def __init__(
         cache_regions=False,
         asynchronous=False,
         loop=None,
-        max_concurrency=1,
+        max_concurrency=10,
         fixed_upload_size: bool = False,
         **kwargs,
     ):
@@ -1133,8 +1133,11 @@ async def _call_and_read():
 
         return await _error_wrapper(_call_and_read, retries=self.retries)
 
-    async def _pipe_file(self, path, data, chunksize=50 * 2**20, **kwargs):
+    async def _pipe_file(
+        self, path, data, chunksize=50 * 2**20, max_concurrency=None, **kwargs
+    ):
         bucket, key, _ = self.split_path(path)
+        concurrency = max_concurrency or self.max_concurrency
         size = len(data)
         # 5 GB is the limit for an S3 PUT
         if size < min(5 * 2**30, 2 * chunksize):
@@ -1146,23 +1149,27 @@ async def _pipe_file(self, path, data, chunksize=50 * 2**20, **kwargs):
             mpu = await self._call_s3(
                 "create_multipart_upload", Bucket=bucket, Key=key, **kwargs
             )
-
-            # TODO: cancel MPU if the following fails
-            out = [
-                await self._call_s3(
-                    "upload_part",
-                    Bucket=bucket,
-                    PartNumber=i + 1,
-                    UploadId=mpu["UploadId"],
-                    Body=data[off : off + chunksize],
-                    Key=key,
+            ranges = list(range(0, len(data), chunksize))
+            inds = list(range(0, len(ranges), concurrency)) + [len(ranges)]
+            parts = []
+            for start, stop in zip(inds[:-1], inds[1:]):
+                out = await asyncio.gather(
+                    *[
+                        self._call_s3(
+                            "upload_part",
+                            Bucket=bucket,
+                            PartNumber=i + 1,
+                            UploadId=mpu["UploadId"],
+                            Body=data[ranges[i] : ranges[i] + chunksize],
+                            Key=key,
+                        )
+                        for i in range(start, stop)
+                    ]
+                )
+                parts.extend(
+                    {"PartNumber": i + 1, "ETag": o["ETag"]}
+                    for i, o in zip(range(start, stop), out)
                 )
-                for i, off in enumerate(range(0, len(data), chunksize))
-            ]
-
-            parts = [
-                {"PartNumber": i + 1, "ETag": o["ETag"]} for i, o in enumerate(out)
-            ]
             await self._call_s3(
                 "complete_multipart_upload",
                 Bucket=bucket,
@@ -2145,7 +2152,7 @@ def __init__(
         s3,
         path,
         mode="rb",
-        block_size=5 * 2**20,
+        block_size=50 * 2**20,
         acl=False,
         version_id=None,
         fill_cache=True,
@@ -2365,6 +2372,7 @@ def n_bytes_left() -> int:
                 return len(self.buffer.getbuffer()) - self.buffer.tell()
 
             min_chunk = 1 if final else self.blocksize
+            # TODO: concurrent here
             if self.fs.fixed_upload_size:
                 # all chunks have fixed size, exception: last one can be smaller
                 while n_bytes_left() >= min_chunk:
diff --git a/s3fs/tests/derived/s3fs_fixtures.py b/s3fs/tests/derived/s3fs_fixtures.py
index eae000cf..a1ca7fb9 100644
--- a/s3fs/tests/derived/s3fs_fixtures.py
+++ b/s3fs/tests/derived/s3fs_fixtures.py
@@ -11,7 +11,7 @@
 test_bucket_name = "test"
 secure_bucket_name = "test-secure"
 versioned_bucket_name = "test-versioned"
-port = 5555
+port = 5556
 endpoint_uri = "http://127.0.0.1:%s/" % port
 
 
@@ -109,6 +109,9 @@ def _s3_base(self):
                 pass
             timeout -= 0.1
             time.sleep(0.1)
+            if proc.poll() is not None:
+                proc.terminate()
+                raise RuntimeError("Starting moto server failed")
         print("server up")
         yield
         print("moto done")
diff --git a/s3fs/tests/test_s3fs.py b/s3fs/tests/test_s3fs.py
index 2275519a..970d2b29 100644
--- a/s3fs/tests/test_s3fs.py
+++ b/s3fs/tests/test_s3fs.py
@@ -90,7 +90,10 @@ def s3_base():
 def reset_s3_fixture():
     # We reuse the MotoServer for all tests
     # But we do want a clean state for every test
-    requests.post(f"{endpoint_uri}/moto-api/reset")
+    try:
+        requests.post(f"{endpoint_uri}/moto-api/reset")
+    except:
+        pass
 
 
 def get_boto3_client():
@@ -1253,7 +1256,7 @@ def test_write_fails(s3):
 
 
 def test_write_blocks(s3):
-    with s3.open(test_bucket_name + "/temp", "wb") as f:
+    with s3.open(test_bucket_name + "/temp", "wb", block_size=5 * 2**20) as f:
         f.write(b"a" * 2 * 2**20)
         assert f.buffer.tell() == 2 * 2**20
         assert not (f.parts)
@@ -1787,7 +1790,7 @@ def test_change_defaults_only_subsequent():
         S3FileSystem.cachable = False  # don't reuse instances with same pars
 
         fs_default = S3FileSystem(client_kwargs={"endpoint_url": endpoint_uri})
-        assert fs_default.default_block_size == 5 * (1024**2)
+        assert fs_default.default_block_size == 50 * (1024**2)
 
         fs_overridden = S3FileSystem(
             default_block_size=64 * (1024**2),
@@ -1804,7 +1807,7 @@ def test_change_defaults_only_subsequent():
 
         # Test the other file systems created to see if their block sizes changed
         assert fs_overridden.default_block_size == 64 * (1024**2)
-        assert fs_default.default_block_size == 5 * (1024**2)
+        assert fs_default.default_block_size == 50 * (1024**2)
     finally:
         S3FileSystem.default_block_size = 5 * (1024**2)
         S3FileSystem.cachable = True