diff --git a/requirements-swh.txt b/requirements-swh.txt
--- a/requirements-swh.txt
+++ b/requirements-swh.txt
@@ -1,3 +1,3 @@
 swh.core[http] >= 0.3
 swh.model >= 0.0.27
-swh.perfecthash
+swh.perfecthash >= 0.1.2
diff --git a/swh/objstorage/backends/winery/objstorage.py b/swh/objstorage/backends/winery/objstorage.py
--- a/swh/objstorage/backends/winery/objstorage.py
+++ b/swh/objstorage/backends/winery/objstorage.py
@@ -6,8 +6,9 @@
 import logging
 from multiprocessing import Process
 
+from swh.model import hashutil
 from swh.objstorage import exc
-from swh.objstorage.objstorage import ObjStorage, compute_hash
+from swh.objstorage.objstorage import ObjStorage
 
 from .roshard import ROShard
 from .rwshard import RWShard
@@ -17,6 +18,11 @@
 logger = logging.getLogger(__name__)
 
 
+def compute_hash(content):
+    algo = "sha256"
+    return hashutil.MultiHash.from_data(content, hash_names=[algo],).digest().get(algo)
+
+
 class WineryObjStorage(ObjStorage):
     def __init__(self, **kwargs):
         super().__init__(**kwargs)
@@ -63,10 +69,16 @@
 
 
 class WineryReader(WineryBase):
+    def __init__(self, **kwargs):
+        super().__init__(**kwargs)
+        self.shards = {}
+
     def roshard(self, name):
-        shard = ROShard(name, **self.args)
-        shard.load()
-        return shard
+        if name not in self.shards:
+            shard = ROShard(name, **self.args)
+            shard.load()
+            self.shards[name] = shard
+        return self.shards[name]
 
     def get(self, obj_id):
         shard_info = self.base.get(obj_id)
diff --git a/swh/objstorage/tests/test_objstorage_winery.py b/swh/objstorage/tests/test_objstorage_winery.py
--- a/swh/objstorage/tests/test_objstorage_winery.py
+++ b/swh/objstorage/tests/test_objstorage_winery.py
@@ -96,7 +96,10 @@
     shard = winery.base.whoami
     content = b"SOMETHING"
     obj_id = winery.add(content=content)
-    assert obj_id.hex() == "0c8c841f7d9fd4874d841506d3ffc16808b1d579"
+    assert (
+        obj_id.hex()
+        == "866878b165607851782d8d233edf0c261172ff67926330d3bbd10c705b92d24f"
+    )
     assert winery.add(content=content, obj_id=obj_id) == obj_id
     assert winery.add(content=content, obj_id=obj_id, check_presence=False) == obj_id
     assert winery.base.whoami == shard
@@ -112,7 +115,10 @@
     shard = winery.base.whoami
     content = b"SOMETHING"
     obj_id = winery.add(content=content)
-    assert obj_id.hex() == "0c8c841f7d9fd4874d841506d3ffc16808b1d579"
+    assert (
+        obj_id.hex()
+        == "866878b165607851782d8d233edf0c261172ff67926330d3bbd10c705b92d24f"
+    )
     assert winery.base.whoami != shard
     assert len(winery.packers) == 1
     packer = winery.packers[0]
diff --git a/winery-test-environment/grid5000.yml b/winery-test-environment/grid5000.yml
--- a/winery-test-environment/grid5000.yml
+++ b/winery-test-environment/grid5000.yml
@@ -39,11 +39,14 @@
   tasks:
 
     # do that before lvm gets a chance to investigate and get the wrong idea
-    # about /dev/sdc on grid5000 because there surely will be leftovers from
+    # about /dev/disk2 on grid5000 because there surely will be leftovers from
     # whoever used the machine last
-    - name: zap /dev/sdc
+    - name: clear leftovers from the disk to be used for OSDs
       shell: |
-        dd if=/dev/zero of=/dev/sdc count=100 bs=1024k
+        dd if=/dev/zero of=/dev/disk2 count=100 bs=1024k
+        touch /etc/dd.done
+      args:
+        creates: /etc/dd.done
 
 - hosts: all
   become: true
diff --git a/winery-test-environment/osd.yml b/winery-test-environment/osd.yml
--- a/winery-test-environment/osd.yml
+++ b/winery-test-environment/osd.yml
@@ -33,8 +33,8 @@
 
     # the desired side effect here is twofold
     # * device zap blocks until the osd daemon is ready on the target host
-    # * on grid5000 /dev/sdc needs to be applied
-    - name: zap /dev/sdc
+    # * on grid5000 /dev/disk2 needs to be applied
+    - name: zap /dev/disk2
       shell: |
-        ceph orch device zap {{ inventory_hostname }} /dev/sdc --force || true
+        ceph orch device zap {{ inventory_hostname }} /dev/disk2 --force || true
       delegate_to: ceph1