diff --git a/cluster_client.cpp b/cluster_client.cpp
index 324bb95d..a460a61f 100644
--- a/cluster_client.cpp
+++ b/cluster_client.cpp
@@ -446,15 +446,7 @@ bool cluster_client_t::try_send(cluster_op_t *op, cluster_op_part_t *part)
                     handle_op_part(part);
                 },
             };
-            part->op.send_list.push_back(part->op.req.buf, OSD_PACKET_SIZE);
-            if (op->opcode == OSD_OP_WRITE)
-            {
-                part->op.send_list.push_back(part->buf, part->len);
-            }
-            else /* if (op->opcode == OSD_OP_READ) */
-            {
-                part->op.buf = part->buf;
-            }
+            part->op.iov.push_back(part->buf, part->len);
             msgr.outbox_push(&part->op);
             return true;
         }
@@ -606,7 +598,6 @@ void cluster_client_t::send_sync(cluster_op_t *op, cluster_op_part_t *part)
             handle_op_part(part);
         },
     };
-    part->op.send_list.push_back(part->op.req.buf, OSD_PACKET_SIZE);
     msgr.outbox_push(&part->op);
 }
 
diff --git a/messenger.cpp b/messenger.cpp
index 1f17ff73..9c867036 100644
--- a/messenger.cpp
+++ b/messenger.cpp
@@ -214,7 +214,6 @@ void osd_messenger_t::check_peer_config(osd_client_t & cl)
 {
     osd_op_t *op = new osd_op_t();
     op->op_type = OSD_OP_OUT;
-    op->send_list.push_back(op->req.buf, OSD_PACKET_SIZE);
     op->peer_fd = cl.peer_fd;
     op->req = {
         .show_conf = {
diff --git a/messenger.h b/messenger.h
index 7d790a44..a5729ca0 100644
--- a/messenger.h
+++ b/messenger.h
@@ -31,13 +31,32 @@
 #define DEFAULT_PEER_CONNECT_INTERVAL 5
 #define DEFAULT_PEER_CONNECT_TIMEOUT 5
 
+// Kind of a vector with small-list-optimisation
 struct osd_op_buf_list_t
 {
-    int count = 0, alloc = 0, sent = 0;
+    int count = 0, alloc = OSD_OP_INLINE_BUF_COUNT, done = 0;
     iovec *buf = NULL;
     iovec inline_buf[OSD_OP_INLINE_BUF_COUNT];
 
-    ~osd_op_buf_list_t()
+    inline osd_op_buf_list_t()
+    {
+        buf = inline_buf;
+    }
+
+    inline osd_op_buf_list_t(const osd_op_buf_list_t & other)
+    {
+        buf = inline_buf;
+        append(other);
+    }
+
+    inline osd_op_buf_list_t & operator = (const osd_op_buf_list_t & other)
+    {
+        reset();
+        append(other);
+        return *this;
+    }
+
+    inline ~osd_op_buf_list_t()
     {
         if (buf && buf != inline_buf)
         {
@@ -45,26 +64,50 @@ struct osd_op_buf_list_t
         }
     }
 
+    inline void reset()
+    {
+        count = 0;
+        done = 0;
+    }
+
     inline iovec* get_iovec()
     {
-        return (buf ? buf : inline_buf) + sent;
+        return buf + done;
     }
 
     inline int get_size()
     {
-        return count - sent;
+        return count - done;
+    }
+
+    inline void append(const osd_op_buf_list_t & other)
+    {
+        if (count+other.count > alloc)
+        {
+            if (buf == inline_buf)
+            {
+                int old = alloc;
+                alloc = (((count+other.count+15)/16)*16);
+                buf = (iovec*)malloc(sizeof(iovec) * alloc);
+                memcpy(buf, inline_buf, sizeof(iovec) * old);
+            }
+            else
+            {
+                alloc = (((count+other.count+15)/16)*16);
+                buf = (iovec*)realloc(buf, sizeof(iovec) * alloc);
+            }
+        }
+        for (int i = 0; i < other.count; i++)
+        {
+            buf[count++] = other.buf[i];
+        }
     }
 
     inline void push_back(void *nbuf, size_t len)
     {
         if (count >= alloc)
         {
-            if (!alloc)
-            {
-                alloc = OSD_OP_INLINE_BUF_COUNT;
-                buf = inline_buf;
-            }
-            else if (buf == inline_buf)
+            if (buf == inline_buf)
             {
                 int old = alloc;
                 alloc = ((alloc/16)*16 + 1);
@@ -79,6 +122,25 @@ struct osd_op_buf_list_t
         }
         buf[count++] = { .iov_base = nbuf, .iov_len = len };
     }
+
+    inline void eat(int result)
+    {
+        while (result > 0 && done < count)
+        {
+            iovec & iov = buf[done];
+            if (iov.iov_len <= result)
+            {
+                result -= iov.iov_len;
+                done++;
+            }
+            else
+            {
+                iov.iov_len -= result;
+                iov.iov_base += result;
+                break;
+            }
+        }
+    }
 };
 
 struct blockstore_op_t;
@@ -98,7 +160,7 @@ struct osd_op_t
     osd_primary_op_data_t* op_data = NULL;
     std::function<void(osd_op_t*)> callback;
 
-    osd_op_buf_list_t send_list;
+    osd_op_buf_list_t iov;
 
     ~osd_op_t();
 };
@@ -117,12 +179,11 @@ struct osd_client_t
     // Read state
     int read_ready = 0;
     osd_op_t *read_op = NULL;
-    int read_reply_id = 0;
     iovec read_iov;
     msghdr read_msg;
-    void *read_buf = NULL;
     int read_remaining = 0;
     int read_state = 0;
+    osd_op_buf_list_t recv_list;
 
     // Incoming operations
     std::vector<osd_op_t*> received_ops;
@@ -138,6 +199,7 @@ struct osd_client_t
     osd_op_t *write_op = NULL;
     msghdr write_msg;
     int write_state = 0;
+    osd_op_buf_list_t send_list;
 };
 
 struct osd_wanted_peer_t
@@ -211,4 +273,5 @@ protected:
     bool handle_finished_read(osd_client_t & cl);
     void handle_op_hdr(osd_client_t *cl);
     bool handle_reply_hdr(osd_client_t *cl);
+    void handle_reply_ready(osd_op_t *op);
 };
diff --git a/msgr_receive.cpp b/msgr_receive.cpp
index 8ddab772..ac0edcfb 100644
--- a/msgr_receive.cpp
+++ b/msgr_receive.cpp
@@ -13,18 +13,20 @@ void osd_messenger_t::read_requests()
             return;
         }
         ring_data_t* data = ((ring_data_t*)sqe->user_data);
-        if (!cl.read_op || cl.read_remaining < receive_buffer_size)
+        if (cl.read_remaining < receive_buffer_size)
         {
             cl.read_iov.iov_base = cl.in_buf;
             cl.read_iov.iov_len = receive_buffer_size;
+            cl.read_msg.msg_iov = &cl.read_iov;
+            cl.read_msg.msg_iovlen = 1;
         }
         else
         {
-            cl.read_iov.iov_base = cl.read_buf;
+            cl.read_iov.iov_base = 0;
             cl.read_iov.iov_len = cl.read_remaining;
+            cl.read_msg.msg_iov = cl.recv_list.get_iovec();
+            cl.read_msg.msg_iovlen = cl.recv_list.get_size();
         }
-        cl.read_msg.msg_iov = &cl.read_iov;
-        cl.read_msg.msg_iovlen = 1;
         data->callback = [this, peer_fd](ring_data_t *data) { handle_read(data->res, peer_fd); };
         my_uring_prep_recvmsg(sqe, peer_fd, &cl.read_msg, 0);
     }
@@ -69,31 +71,33 @@ bool osd_messenger_t::handle_read(int result, int peer_fd)
                         cl.read_op = new osd_op_t;
                         cl.read_op->peer_fd = peer_fd;
                         cl.read_op->op_type = OSD_OP_IN;
-                        cl.read_buf = cl.read_op->req.buf;
+                        cl.recv_list.push_back(cl.read_op->req.buf, OSD_PACKET_SIZE);
                         cl.read_remaining = OSD_PACKET_SIZE;
                         cl.read_state = CL_READ_HDR;
                     }
-                    if (cl.read_remaining > remain)
+                    while (cl.recv_list.done < cl.recv_list.count && remain > 0)
                     {
-                        memcpy(cl.read_buf, curbuf, remain);
-                        cl.read_remaining -= remain;
-                        cl.read_buf += remain;
-                        remain = 0;
-                        if (cl.read_remaining <= 0)
+                        iovec* cur = cl.recv_list.get_iovec();
+                        if (cur->iov_len > remain)
                         {
-                            if (!handle_finished_read(cl))
-                            {
-                                goto fin;
-                            }
+                            memcpy(cur->iov_base, curbuf, remain);
+                            cl.read_remaining -= remain;
+                            cur->iov_len -= remain;
+                            cur->iov_base += remain;
+                            remain = 0;
+                        }
+                        else
+                        {
+                            memcpy(cur->iov_base, curbuf, cur->iov_len);
+                            curbuf += cur->iov_len;
+                            cl.read_remaining -= cur->iov_len;
+                            remain -= cur->iov_len;
+                            cur->iov_len = 0;
+                            cl.recv_list.done++;
                         }
                     }
-                    else
+                    if (cl.recv_list.done >= cl.recv_list.count)
                     {
-                        memcpy(cl.read_buf, curbuf, cl.read_remaining);
-                        curbuf += cl.read_remaining;
-                        remain -= cl.read_remaining;
-                        cl.read_remaining = 0;
-                        cl.read_buf = NULL;
                         if (!handle_finished_read(cl))
                         {
                             goto fin;
@@ -105,8 +109,8 @@ bool osd_messenger_t::handle_read(int result, int peer_fd)
             {
                 // Long data
                 cl.read_remaining -= result;
-                cl.read_buf += result;
-                if (cl.read_remaining <= 0)
+                cl.recv_list.eat(result);
+                if (cl.recv_list.done >= cl.recv_list.count)
                 {
                     handle_finished_read(cl);
                 }
@@ -128,6 +132,7 @@ fin:
 
 bool osd_messenger_t::handle_finished_read(osd_client_t & cl)
 {
+    cl.recv_list.reset();
     if (cl.read_state == CL_READ_HDR)
     {
         if (cl.read_op->req.hdr.magic == SECONDARY_OSD_REPLY_MAGIC)
@@ -146,30 +151,9 @@ bool osd_messenger_t::handle_finished_read(osd_client_t & cl)
     else if (cl.read_state == CL_READ_REPLY_DATA)
     {
         // Reply is ready
-        auto req_it = cl.sent_ops.find(cl.read_reply_id);
-        osd_op_t *request = req_it->second;
-        cl.sent_ops.erase(req_it);
-        cl.read_reply_id = 0;
-        delete cl.read_op;
+        handle_reply_ready(cl.read_op);
         cl.read_op = NULL;
         cl.read_state = 0;
-        // Measure subop latency
-        timespec tv_end;
-        clock_gettime(CLOCK_REALTIME, &tv_end);
-        stats.subop_stat_count[request->req.hdr.opcode]++;
-        if (!stats.subop_stat_count[request->req.hdr.opcode])
-        {
-            stats.subop_stat_count[request->req.hdr.opcode]++;
-            stats.subop_stat_sum[request->req.hdr.opcode] = 0;
-        }
-        stats.subop_stat_sum[request->req.hdr.opcode] += (
-            (tv_end.tv_sec - request->tv_begin.tv_sec)*1000000 +
-            (tv_end.tv_nsec - request->tv_begin.tv_nsec)/1000
-        );
-        set_immediate.push_back([this, request]()
-        {
-            std::function<void(osd_op_t*)>(request->callback)(request);
-        });
     }
     else
     {
@@ -215,82 +199,92 @@ void osd_messenger_t::handle_op_hdr(osd_client_t *cl)
     if (cl->read_remaining > 0)
     {
         // Read data
-        cl->read_buf = cur_op->buf;
+        cl->recv_list.push_back(cur_op->buf, cl->read_remaining);
         cl->read_state = CL_READ_DATA;
     }
     else
     {
         // Operation is ready
-        cl->read_op = NULL;
-        cl->read_state = 0;
         cl->received_ops.push_back(cur_op);
         set_immediate.push_back([this, cur_op]() { exec_op(cur_op); });
+        cl->read_op = NULL;
+        cl->read_state = 0;
     }
 }
 
 bool osd_messenger_t::handle_reply_hdr(osd_client_t *cl)
 {
-    osd_op_t *cur_op = cl->read_op;
-    auto req_it = cl->sent_ops.find(cur_op->req.hdr.id);
+    auto req_it = cl->sent_ops.find(cl->read_op->req.hdr.id);
     if (req_it == cl->sent_ops.end())
     {
         // Command out of sync. Drop connection
-        printf("Client %d command out of sync: id %lu\n", cl->peer_fd, cur_op->req.hdr.id);
+        printf("Client %d command out of sync: id %lu\n", cl->peer_fd, cl->read_op->req.hdr.id);
         stop_client(cl->peer_fd);
         return false;
     }
     osd_op_t *op = req_it->second;
-    memcpy(op->reply.buf, cur_op->req.buf, OSD_PACKET_SIZE);
+    memcpy(op->reply.buf, cl->read_op->req.buf, OSD_PACKET_SIZE);
+    cl->sent_ops.erase(req_it);
     if ((op->reply.hdr.opcode == OSD_OP_SECONDARY_READ || op->reply.hdr.opcode == OSD_OP_READ) &&
         op->reply.hdr.retval > 0)
     {
         // Read data. In this case we assume that the buffer is preallocated by the caller (!)
-        assert(op->buf);
+        assert(op->iov.count > 0);
+        cl->recv_list.append(op->iov);
+        delete cl->read_op;
+        cl->read_op = op;
         cl->read_state = CL_READ_REPLY_DATA;
-        cl->read_reply_id = op->req.hdr.id;
-        cl->read_buf = op->buf;
         cl->read_remaining = op->reply.hdr.retval;
     }
     else if (op->reply.hdr.opcode == OSD_OP_SECONDARY_LIST && op->reply.hdr.retval > 0)
     {
-        op->buf = memalign(MEM_ALIGNMENT, sizeof(obj_ver_id) * op->reply.hdr.retval);
+        assert(!op->iov.count);
+        delete cl->read_op;
+        cl->read_op = op;
         cl->read_state = CL_READ_REPLY_DATA;
-        cl->read_reply_id = op->req.hdr.id;
-        cl->read_buf = op->buf;
         cl->read_remaining = sizeof(obj_ver_id) * op->reply.hdr.retval;
+        op->buf = memalign(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)
     {
-        op->buf = malloc(op->reply.hdr.retval);
+        assert(!op->iov.count);
+        delete cl->read_op;
+        cl->read_op = op;
         cl->read_state = CL_READ_REPLY_DATA;
-        cl->read_reply_id = op->req.hdr.id;
-        cl->read_buf = op->buf;
         cl->read_remaining = op->reply.hdr.retval;
+        op->buf = malloc(op->reply.hdr.retval);
+        cl->recv_list.push_back(op->buf, op->reply.hdr.retval);
     }
     else
     {
-        delete cl->read_op;
-        cl->read_state = 0;
-        cl->read_op = NULL;
-        cl->sent_ops.erase(req_it);
-        // Measure subop latency
-        timespec tv_end;
-        clock_gettime(CLOCK_REALTIME, &tv_end);
-        stats.subop_stat_count[op->req.hdr.opcode]++;
-        if (!stats.subop_stat_count[op->req.hdr.opcode])
-        {
-            stats.subop_stat_count[op->req.hdr.opcode]++;
-            stats.subop_stat_sum[op->req.hdr.opcode] = 0;
-        }
-        stats.subop_stat_sum[op->req.hdr.opcode] += (
-            (tv_end.tv_sec - op->tv_begin.tv_sec)*1000000 +
-            (tv_end.tv_nsec - op->tv_begin.tv_nsec)/1000
-        );
-        set_immediate.push_back([this, op]()
-        {
-            // Copy lambda to be unaffected by `delete op`
-            std::function<void(osd_op_t*)>(op->callback)(op);
-        });
+        // It's fine to reuse cl->read_op for the next reply
+        handle_reply_ready(op);
+        cl->recv_list.push_back(cl->read_op->req.buf, OSD_PACKET_SIZE);
+        cl->read_remaining = OSD_PACKET_SIZE;
+        cl->read_state = CL_READ_HDR;
     }
     return true;
 }
+
+void osd_messenger_t::handle_reply_ready(osd_op_t *op)
+{
+    // Measure subop latency
+    timespec tv_end;
+    clock_gettime(CLOCK_REALTIME, &tv_end);
+    stats.subop_stat_count[op->req.hdr.opcode]++;
+    if (!stats.subop_stat_count[op->req.hdr.opcode])
+    {
+        stats.subop_stat_count[op->req.hdr.opcode]++;
+        stats.subop_stat_sum[op->req.hdr.opcode] = 0;
+    }
+    stats.subop_stat_sum[op->req.hdr.opcode] += (
+        (tv_end.tv_sec - op->tv_begin.tv_sec)*1000000 +
+        (tv_end.tv_nsec - op->tv_begin.tv_nsec)/1000
+    );
+    set_immediate.push_back([this, op]()
+    {
+        // Copy lambda to be unaffected by `delete op`
+        std::function<void(osd_op_t*)>(op->callback)(op);
+    });
+}
diff --git a/msgr_send.cpp b/msgr_send.cpp
index 420e4234..0f9fde6e 100644
--- a/msgr_send.cpp
+++ b/msgr_send.cpp
@@ -80,10 +80,29 @@ bool osd_messenger_t::try_send(osd_client_t & cl)
             {
                 stats.op_stat_bytes[cl.write_op->req.hdr.opcode] += cl.write_op->req.sec_rw.len;
             }
+            cl.send_list.push_back(cl.write_op->reply.buf, OSD_PACKET_SIZE);
+            if (cl.write_op->req.hdr.opcode == OSD_OP_READ ||
+                cl.write_op->req.hdr.opcode == OSD_OP_SECONDARY_READ ||
+                cl.write_op->req.hdr.opcode == OSD_OP_SECONDARY_LIST ||
+                cl.write_op->req.hdr.opcode == OSD_OP_SHOW_CONFIG)
+            {
+                cl.send_list.append(cl.write_op->iov);
+            }
+        }
+        else
+        {
+            cl.send_list.push_back(cl.write_op->req.buf, OSD_PACKET_SIZE);
+            if (cl.write_op->req.hdr.opcode == OSD_OP_WRITE ||
+                cl.write_op->req.hdr.opcode == OSD_OP_SECONDARY_WRITE ||
+                cl.write_op->req.hdr.opcode == OSD_OP_SECONDARY_STABILIZE ||
+                cl.write_op->req.hdr.opcode == OSD_OP_SECONDARY_ROLLBACK)
+            {
+                cl.send_list.append(cl.write_op->iov);
+            }
         }
     }
-    cl.write_msg.msg_iov = cl.write_op->send_list.get_iovec();
-    cl.write_msg.msg_iovlen = cl.write_op->send_list.get_size();
+    cl.write_msg.msg_iov = cl.send_list.get_iovec();
+    cl.write_msg.msg_iovlen = cl.send_list.get_size();
     data->callback = [this, peer_fd](ring_data_t *data) { handle_send(data->res, peer_fd); };
     my_uring_prep_sendmsg(sqe, peer_fd, &cl.write_msg, 0);
     return true;
@@ -118,28 +137,14 @@ void osd_messenger_t::handle_send(int result, int peer_fd)
         }
         if (result >= 0)
         {
-            osd_op_t *cur_op = cl.write_op;
-            while (result > 0 && cur_op->send_list.sent < cur_op->send_list.count)
-            {
-                iovec & iov = cur_op->send_list.buf[cur_op->send_list.sent];
-                if (iov.iov_len <= result)
-                {
-                    result -= iov.iov_len;
-                    cur_op->send_list.sent++;
-                }
-                else
-                {
-                    iov.iov_len -= result;
-                    iov.iov_base += result;
-                    break;
-                }
-            }
-            if (cur_op->send_list.sent >= cur_op->send_list.count)
+            cl.send_list.eat(result);
+            if (cl.send_list.done >= cl.send_list.count)
             {
                 // Done
-                if (cur_op->op_type == OSD_OP_IN)
+                cl.send_list.reset();
+                if (cl.write_op->op_type == OSD_OP_IN)
                 {
-                    delete cur_op;
+                    delete cl.write_op;
                 }
                 else
                 {
diff --git a/osd.cpp b/osd.cpp
index f73dec79..da9f48ae 100644
--- a/osd.cpp
+++ b/osd.cpp
@@ -289,7 +289,6 @@ void osd_t::exec_op(osd_op_t *cur_op)
         return;
     }
     inflight_ops++;
-    cur_op->send_list.push_back(cur_op->reply.buf, OSD_PACKET_SIZE);
     if (cur_op->req.hdr.magic != SECONDARY_OSD_OP_MAGIC ||
         cur_op->req.hdr.opcode < OSD_OP_MIN || cur_op->req.hdr.opcode > OSD_OP_MAX ||
         (cur_op->req.hdr.opcode == OSD_OP_SECONDARY_READ || cur_op->req.hdr.opcode == OSD_OP_SECONDARY_WRITE) &&
diff --git a/osd_flush.cpp b/osd_flush.cpp
index 0fe46a0a..687bfe67 100644
--- a/osd_flush.cpp
+++ b/osd_flush.cpp
@@ -183,8 +183,7 @@ void osd_t::submit_flush_op(pg_num_t pg_num, pg_flush_batch_t *fb, bool rollback
         // Peer
         int peer_fd = c_cli.osd_peer_fds[peer_osd];
         op->op_type = OSD_OP_OUT;
-        op->send_list.push_back(op->req.buf, OSD_PACKET_SIZE);
-        op->send_list.push_back(op->buf, count * sizeof(obj_ver_id));
+        op->iov.push_back(op->buf, count * sizeof(obj_ver_id));
         op->peer_fd = peer_fd;
         op->req = {
             .sec_stab = {
diff --git a/osd_peering.cpp b/osd_peering.cpp
index 5e5f1614..b0721787 100644
--- a/osd_peering.cpp
+++ b/osd_peering.cpp
@@ -303,7 +303,6 @@ void osd_t::submit_sync_and_list_subop(osd_num_t role_osd, pg_peering_state_t *p
         auto & cl = c_cli.clients.at(c_cli.osd_peer_fds[role_osd]);
         osd_op_t *op = new osd_op_t();
         op->op_type = OSD_OP_OUT;
-        op->send_list.push_back(op->req.buf, OSD_PACKET_SIZE);
         op->peer_fd = cl.peer_fd;
         op->req = {
             .sec_sync = {
@@ -377,7 +376,6 @@ void osd_t::submit_list_subop(osd_num_t role_osd, pg_peering_state_t *ps)
         // Peer
         osd_op_t *op = new osd_op_t();
         op->op_type = OSD_OP_OUT;
-        op->send_list.push_back(op->req.buf, OSD_PACKET_SIZE);
         op->peer_fd = c_cli.osd_peer_fds[role_osd];
         op->req = {
             .sec_list = {
diff --git a/osd_primary.cpp b/osd_primary.cpp
index 93928322..c83294d9 100644
--- a/osd_primary.cpp
+++ b/osd_primary.cpp
@@ -142,7 +142,7 @@ resume_2:
             if (stripes[role].req_end != 0)
             {
                 // Send buffer in parts to avoid copying
-                cur_op->send_list.push_back(
+                cur_op->iov.push_back(
                     stripes[role].read_buf + (stripes[role].req_start - stripes[role].read_start),
                     stripes[role].req_end - stripes[role].req_start
                 );
@@ -151,7 +151,7 @@ resume_2:
     }
     else
     {
-        cur_op->send_list.push_back(cur_op->buf, cur_op->req.rw.len);
+        cur_op->iov.push_back(cur_op->buf, cur_op->req.rw.len);
     }
     finish_op(cur_op, cur_op->req.rw.len);
 }
diff --git a/osd_primary_subops.cpp b/osd_primary_subops.cpp
index ccff4dc9..a99776d8 100644
--- a/osd_primary_subops.cpp
+++ b/osd_primary_subops.cpp
@@ -150,7 +150,6 @@ void osd_t::submit_primary_subops(int submit_type, int pg_size, const uint64_t*
             else
             {
                 subops[i].op_type = OSD_OP_OUT;
-                subops[i].send_list.push_back(subops[i].req.buf, OSD_PACKET_SIZE);
                 subops[i].peer_fd = c_cli.osd_peer_fds.at(role_osd_num);
                 subops[i].req.sec_rw = {
                     .header = {
@@ -173,17 +172,24 @@ void osd_t::submit_primary_subops(int submit_type, int pg_size, const uint64_t*
                     subops[i].req.sec_rw.offset, subops[i].req.sec_rw.len
                 );
 #endif
-                subops[i].buf = w ? stripes[role].write_buf : stripes[role].read_buf;
-                if (w && stripes[role].write_end > 0)
+                if (w)
                 {
-                    subops[i].send_list.push_back(stripes[role].write_buf, stripes[role].write_end - stripes[role].write_start);
+                    if (stripes[role].write_end > stripes[role].write_start)
+                    {
+                        subops[i].iov.push_back(stripes[role].write_buf, stripes[role].write_end - stripes[role].write_start);
+                    }
+                }
+                else
+                {
+                    if (stripes[role].read_end > stripes[role].read_start)
+                    {
+                        subops[i].iov.push_back(stripes[role].read_buf, stripes[role].read_end - stripes[role].read_start);
+                    }
                 }
                 subops[i].callback = [cur_op, this](osd_op_t *subop)
                 {
                     int fail_fd = subop->req.hdr.opcode == OSD_OP_SECONDARY_WRITE &&
                         subop->reply.hdr.retval != subop->req.sec_rw.len ? subop->peer_fd : -1;
-                    // so it doesn't get freed
-                    subop->buf = NULL;
                     handle_primary_subop(subop, cur_op);
                     if (fail_fd >= 0)
                     {
@@ -387,7 +393,6 @@ void osd_t::submit_primary_del_subops(osd_op_t *cur_op, uint64_t *cur_set, pg_os
             else
             {
                 subops[i].op_type = OSD_OP_OUT;
-                subops[i].send_list.push_back(subops[i].req.buf, OSD_PACKET_SIZE);
                 subops[i].peer_fd = c_cli.osd_peer_fds.at(chunk.osd_num);
                 subops[i].req.sec_del = {
                     .header = {
@@ -446,7 +451,6 @@ void osd_t::submit_primary_sync_subops(osd_op_t *cur_op)
         else
         {
             subops[i].op_type = OSD_OP_OUT;
-            subops[i].send_list.push_back(subops[i].req.buf, OSD_PACKET_SIZE);
             subops[i].peer_fd = c_cli.osd_peer_fds.at(sync_osd);
             subops[i].req.sec_sync = {
                 .header = {
@@ -499,7 +503,6 @@ void osd_t::submit_primary_stab_subops(osd_op_t *cur_op)
         else
         {
             subops[i].op_type = OSD_OP_OUT;
-            subops[i].send_list.push_back(subops[i].req.buf, OSD_PACKET_SIZE);
             subops[i].peer_fd = c_cli.osd_peer_fds.at(stab_osd.osd_num);
             subops[i].req.sec_stab = {
                 .header = {
@@ -509,7 +512,7 @@ void osd_t::submit_primary_stab_subops(osd_op_t *cur_op)
                 },
                 .len = (uint64_t)(stab_osd.len * sizeof(obj_ver_id)),
             };
-            subops[i].send_list.push_back(op_data->unstable_writes + stab_osd.start, stab_osd.len * sizeof(obj_ver_id));
+            subops[i].iov.push_back(op_data->unstable_writes + stab_osd.start, stab_osd.len * sizeof(obj_ver_id));
             subops[i].callback = [cur_op, this](osd_op_t *subop)
             {
                 int fail_fd = subop->reply.hdr.retval != 0 ? subop->peer_fd : -1;
diff --git a/osd_secondary.cpp b/osd_secondary.cpp
index 30facebe..480d8685 100644
--- a/osd_secondary.cpp
+++ b/osd_secondary.cpp
@@ -16,7 +16,7 @@ void osd_t::secondary_op_callback(osd_op_t *op)
     if (op->req.hdr.opcode == OSD_OP_SECONDARY_READ &&
         op->bs_op->retval > 0)
     {
-        op->send_list.push_back(op->buf, op->bs_op->retval);
+        op->iov.push_back(op->buf, op->bs_op->retval);
     }
     else if (op->req.hdr.opcode == OSD_OP_SECONDARY_LIST)
     {
@@ -24,7 +24,7 @@ void osd_t::secondary_op_callback(osd_op_t *op)
         op->buf = op->bs_op->buf;
         if (op->bs_op->retval > 0)
         {
-            op->send_list.push_back(op->buf, op->bs_op->retval * sizeof(obj_ver_id));
+            op->iov.push_back(op->buf, op->bs_op->retval * sizeof(obj_ver_id));
         }
         op->reply.sec_list.stable_count = op->bs_op->version;
     }
@@ -105,7 +105,7 @@ void osd_t::exec_show_config(osd_op_t *cur_op)
     std::string cfg_str = json11::Json(config).dump();
     cur_op->buf = malloc(cfg_str.size()+1);
     memcpy(cur_op->buf, cfg_str.c_str(), cfg_str.size()+1);
-    cur_op->send_list.push_back(cur_op->buf, cfg_str.size()+1);
+    cur_op->iov.push_back(cur_op->buf, cfg_str.size()+1);
     finish_op(cur_op, cfg_str.size()+1);
 }
 
diff --git a/stub_uring_osd.cpp b/stub_uring_osd.cpp
index 07a9b777..c05253e5 100644
--- a/stub_uring_osd.cpp
+++ b/stub_uring_osd.cpp
@@ -105,12 +105,11 @@ void stub_exec_op(osd_messenger_t *msgr, osd_op_t *op)
     op->reply.hdr.magic = SECONDARY_OSD_REPLY_MAGIC;
     op->reply.hdr.id = op->req.hdr.id;
     op->reply.hdr.opcode = op->req.hdr.opcode;
-    op->send_list.push_back(op->reply.buf, OSD_PACKET_SIZE);
     if (op->req.hdr.opcode == OSD_OP_SECONDARY_READ)
     {
         op->reply.hdr.retval = op->req.sec_rw.len;
         op->buf = malloc(op->req.sec_rw.len);
-        op->send_list.push_back(op->buf, op->req.sec_rw.len);
+        op->iov.push_back(op->buf, op->req.sec_rw.len);
     }
     else if (op->req.hdr.opcode == OSD_OP_SECONDARY_WRITE)
     {