diff --git a/src/msgr_receive.cpp b/src/msgr_receive.cpp
index afcd2a0c..8be182cf 100644
--- a/src/msgr_receive.cpp
+++ b/src/msgr_receive.cpp
@@ -232,6 +232,15 @@ void osd_messenger_t::handle_op_hdr(osd_client_t *cl)
         }
         cl->read_remaining = cur_op->req.sec_stab.len;
     }
+    else if (cur_op->req.hdr.opcode == OSD_OP_SEC_READ_BMP)
+    {
+        if (cur_op->req.sec_read_bmp.len > 0)
+        {
+            cur_op->buf = memalign_or_die(MEM_ALIGNMENT, cur_op->req.sec_read_bmp.len);
+            cl->recv_list.push_back(cur_op->buf, cur_op->req.sec_read_bmp.len);
+        }
+        cl->read_remaining = cur_op->req.sec_read_bmp.len;
+    }
     else if (cur_op->req.hdr.opcode == OSD_OP_READ)
     {
         cl->read_remaining = 0;
@@ -277,17 +286,19 @@ bool osd_messenger_t::handle_reply_hdr(osd_client_t *cl)
     {
         // Read data. In this case we assume that the buffer is preallocated by the caller (!)
         unsigned bmp_len = (op->reply.hdr.opcode == OSD_OP_SEC_READ ? op->reply.sec_rw.attr_len : op->reply.rw.bitmap_len);
-        if (op->reply.hdr.retval != (op->reply.hdr.opcode == OSD_OP_SEC_READ ? op->req.sec_rw.len : op->req.rw.len) ||
-            bmp_len > op->bitmap_len)
+        unsigned expected_size = (op->reply.hdr.opcode == OSD_OP_SEC_READ ? op->req.sec_rw.len : op->req.rw.len);
+        if (op->reply.hdr.retval >= 0 && (op->reply.hdr.retval != expected_size || bmp_len > op->bitmap_len))
         {
             // Check reply length to not overflow the buffer
-            printf("Client %d read reply of different length\n", cl->peer_fd);
+            printf("Client %d read reply of different length: expected %u+%u, got %ld+%u\n",
+                cl->peer_fd, expected_size, op->bitmap_len, op->reply.hdr.retval, bmp_len);
             cl->sent_ops[op->req.hdr.id] = op;
             stop_client(cl->peer_fd);
             return false;
         }
-        if (bmp_len > 0)
+        if (op->reply.hdr.retval >= 0 && bmp_len > 0)
         {
+            assert(op->bitmap);
             cl->recv_list.push_back(op->bitmap, bmp_len);
         }
         if (op->reply.hdr.retval > 0)
@@ -314,6 +325,16 @@ bool osd_messenger_t::handle_reply_hdr(osd_client_t *cl)
         op->buf = memalign_or_die(MEM_ALIGNMENT, cl->read_remaining);
         cl->recv_list.push_back(op->buf, cl->read_remaining);
     }
+    else if (op->reply.hdr.opcode == OSD_OP_SEC_READ_BMP && op->reply.hdr.retval > 0)
+    {
+        assert(!op->iov.count);
+        delete cl->read_op;
+        cl->read_op = op;
+        cl->read_state = CL_READ_REPLY_DATA;
+        cl->read_remaining = op->reply.hdr.retval;
+        op->buf = memalign_or_die(MEM_ALIGNMENT, cl->read_remaining);
+        cl->recv_list.push_back(op->buf, cl->read_remaining);
+    }
     else if (op->reply.hdr.opcode == OSD_OP_SHOW_CONFIG && op->reply.hdr.retval > 0)
     {
         assert(!op->iov.count);
diff --git a/src/msgr_send.cpp b/src/msgr_send.cpp
index 115d5edc..8bdaf197 100644
--- a/src/msgr_send.cpp
+++ b/src/msgr_send.cpp
@@ -87,6 +87,14 @@ void osd_messenger_t::outbox_push(osd_op_t *cur_op)
             to_outbox.push_back(NULL);
         }
     }
+    if (cur_op->req.hdr.opcode == OSD_OP_SEC_READ_BMP)
+    {
+        if (cur_op->op_type == OSD_OP_IN && cur_op->reply.hdr.retval > 0)
+            to_send_list.push_back((iovec){ .iov_base = cur_op->buf, .iov_len = (size_t)cur_op->reply.hdr.retval });
+        else if (cur_op->op_type == OSD_OP_OUT && cur_op->req.sec_read_bmp.len > 0)
+            to_send_list.push_back((iovec){ .iov_base = cur_op->buf, .iov_len = (size_t)cur_op->req.sec_read_bmp.len });
+        to_outbox.push_back(NULL);
+    }
     if (cur_op->op_type == OSD_OP_IN)
     {
         // To free it later
diff --git a/src/osd.cpp b/src/osd.cpp
index d470c72f..523f9c11 100644
--- a/src/osd.cpp
+++ b/src/osd.cpp
@@ -231,6 +231,7 @@ void osd_t::exec_op(osd_op_t *cur_op)
         cur_op->req.hdr.opcode != OSD_OP_SEC_READ &&
         cur_op->req.hdr.opcode != OSD_OP_SEC_LIST &&
         cur_op->req.hdr.opcode != OSD_OP_READ &&
+        cur_op->req.hdr.opcode != OSD_OP_SEC_READ_BMP &&
         cur_op->req.hdr.opcode != OSD_OP_SHOW_CONFIG)
     {
         // Readonly mode
diff --git a/src/osd_ops.cpp b/src/osd_ops.cpp
index 0d8b1214..e2aa7bce 100644
--- a/src/osd_ops.cpp
+++ b/src/osd_ops.cpp
@@ -20,4 +20,5 @@ const char* osd_op_names[] = {
     "primary_sync",
     "primary_delete",
     "ping",
+    "sec_read_bmp",
 };
diff --git a/src/osd_ops.h b/src/osd_ops.h
index 1d81f3af..94b185d0 100644
--- a/src/osd_ops.h
+++ b/src/osd_ops.h
@@ -28,7 +28,8 @@
 #define OSD_OP_SYNC                 13
 #define OSD_OP_DELETE               14
 #define OSD_OP_PING                 15
-#define OSD_OP_MAX                  15
+#define OSD_OP_SEC_READ_BMP         16
+#define OSD_OP_MAX                  16
 // Alignment & limit for read/write operations
 #ifndef MEM_ALIGNMENT
 #define MEM_ALIGNMENT               512
@@ -128,6 +129,20 @@ struct __attribute__((__packed__)) osd_reply_sec_stab_t
 };
 typedef osd_reply_sec_stab_t osd_reply_sec_rollback_t;
 
+// bulk read bitmaps from a secondary OSD
+struct __attribute__((__packed__)) osd_op_sec_read_bmp_t
+{
+    osd_op_header_t header;
+    // obj_ver_id array length in bytes
+    uint64_t len;
+};
+
+struct __attribute__((__packed__)) osd_reply_sec_read_bmp_t
+{
+    // retval is payload length in bytes. payload is {version,bitmap}[]
+    osd_reply_header_t header;
+};
+
 // show configuration
 struct __attribute__((__packed__)) osd_op_show_config_t
 {
@@ -198,6 +213,7 @@ union osd_any_op_t
     osd_op_sec_del_t sec_del;
     osd_op_sec_sync_t sec_sync;
     osd_op_sec_stab_t sec_stab;
+    osd_op_sec_read_bmp_t sec_read_bmp;
     osd_op_sec_list_t sec_list;
     osd_op_show_config_t show_conf;
     osd_op_rw_t rw;
@@ -212,6 +228,7 @@ union osd_any_reply_t
     osd_reply_sec_del_t sec_del;
     osd_reply_sec_sync_t sec_sync;
     osd_reply_sec_stab_t sec_stab;
+    osd_reply_sec_read_bmp_t sec_read_bmp;
     osd_reply_sec_list_t sec_list;
     osd_reply_show_config_t show_conf;
     osd_reply_rw_t rw;
diff --git a/src/osd_secondary.cpp b/src/osd_secondary.cpp
index 02331c51..5f4fb46f 100644
--- a/src/osd_secondary.cpp
+++ b/src/osd_secondary.cpp
@@ -44,6 +44,25 @@ void osd_t::secondary_op_callback(osd_op_t *op)
 
 void osd_t::exec_secondary(osd_op_t *cur_op)
 {
+    if (cur_op->req.hdr.opcode == OSD_OP_SEC_READ_BMP)
+    {
+        int n = cur_op->req.sec_read_bmp.len / sizeof(obj_ver_id);
+        if (n > 0)
+        {
+            obj_ver_id *ov = (obj_ver_id*)cur_op->buf;
+            void *reply_buf = malloc_or_die(n * (8 + clean_entry_bitmap_size));
+            void *cur_buf = reply_buf;
+            for (int i = 0; i < n; i++)
+            {
+                bs->read_bitmap(ov[i].oid, ov[i].version, cur_buf + sizeof(uint64_t), (uint64_t*)cur_buf);
+                cur_buf += (8 + clean_entry_bitmap_size);
+            }
+            free(cur_op->buf);
+            cur_op->buf = reply_buf;
+        }
+        finish_op(cur_op, n * (8 + clean_entry_bitmap_size));
+        return;
+    }
     cur_op->bs_op = new blockstore_op_t();
     cur_op->bs_op->callback = [this, cur_op](blockstore_op_t* bs_op) { secondary_op_callback(cur_op); };
     cur_op->bs_op->opcode = (cur_op->req.hdr.opcode == OSD_OP_SEC_READ ? BS_OP_READ