diff --git a/build_merged_v2.py b/build_merged_v2.py
new file mode 100644
index 0000000..eefc8f6
--- /dev/null
+++ b/build_merged_v2.py
@@ -0,0 +1,92 @@
+#!/usr/bin/env python3
+"""
+Build merged GDT using corrected 5-chunk translation formula.
+
+With the old formula (group*4*CHUNK), chunk_idx=4 blocks were skipped and
+every address past group 0 was wrong. The correct formula is group*5*CHUNK
+for all chunk indices 0-4.
+
+Since all chunks are now readable, we use the primary GDT for everything and
+fall back to the backup (group 1) only when a primary entry reads as all-zeros
+(indicating it genuinely landed in a damaged sector).
+"""
+import struct
+
+CHUNK      = 128 * 512     # 64 KB
+LV_START   = 5120000 * 512
+BSIZE      = 4096
+BPG        = 32768
+GDT_ENTRY  = 64
+NUM_GROUPS = 35728
+
+
+def raw_read(virt_offset, length):
+    """Correct PERC H710 translation — 5-chunk stride, all chunks readable."""
+    result = bytearray(length)
+    pos = virt_offset
+    remaining = length
+    with open('/dev/md0', 'rb') as f:
+        while remaining > 0:
+            group     = pos // (5 * CHUNK)
+            in_group  = pos % (5 * CHUNK)
+            chunk_idx = in_group // CHUNK
+            intra     = in_group % CHUNK
+            seg_len   = min(CHUNK - intra, remaining)
+            dst_off   = pos - virt_offset
+            phys = LV_START + group * 5 * CHUNK + chunk_idx * CHUNK + intra
+            f.seek(phys)
+            data = f.read(seg_len)
+            result[dst_off:dst_off + len(data)] = data
+            pos       += seg_len
+            remaining -= seg_len
+    return bytes(result)
+
+
+print('Building merged GDT (v2 — corrected 5-chunk formula)...')
+primary_start = BSIZE                  # block 1
+backup_start  = (1 * BPG + 1) * BSIZE # group 1 backup SB location
+
+primary_gdt = raw_read(primary_start, NUM_GROUPS * GDT_ENTRY)
+backup_gdt  = raw_read(backup_start,  NUM_GROUPS * GDT_ENTRY)
+
+merged       = bytearray(NUM_GROUPS * GDT_ENTRY)
+primary_used = 0
+backup_used  = 0
+zero_both    = 0
+
+for g in range(NUM_GROUPS):
+    src_off = g * GDT_ENTRY
+    prim_e  = primary_gdt[src_off:src_off + GDT_ENTRY]
+    back_e  = backup_gdt[src_off:src_off + GDT_ENTRY]
+
+    if any(prim_e):
+        merged[src_off:src_off + GDT_ENTRY] = prim_e
+        primary_used += 1
+    elif any(back_e):
+        merged[src_off:src_off + GDT_ENTRY] = back_e
+        backup_used += 1
+    else:
+        zero_both += 1
+
+print(f'  From primary GDT : {primary_used}')
+print(f'  From backup GDT  : {backup_used}')
+print(f'  Both zero (lost) : {zero_both}')
+
+if zero_both > 0:
+    print(f'  WARNING: {zero_both} group descriptors could not be recovered')
+
+print()
+print('Sample entries:')
+for g in [0, 1, 13, 100, 1000, 35000, 35727]:
+    e   = merged[g * GDT_ENTRY:(g + 1) * GDT_ENTRY]
+    bb  = struct.unpack_from('<I', e,  0)[0]
+    ib  = struct.unpack_from('<I', e,  4)[0]
+    it  = struct.unpack_from('<I', e,  8)[0]
+    cs  = struct.unpack_from('<H', e, 30)[0]
+    src = 'primary' if any(primary_gdt[g*GDT_ENTRY:(g+1)*GDT_ENTRY]) else 'backup'
+    print(f'  Group {g:6d}: bb={bb:10d} ib={ib:10d} it={it:10d} '
+          f'csum=0x{cs:04x}  [{src}]')
+
+with open('/tmp/merged_gdt.bin', 'wb') as f:
+    f.write(merged)
+print(f'\nSaved /tmp/merged_gdt.bin ({len(merged) // 1024} KB)')
diff --git a/nbd_server_v10.py b/nbd_server_v10.py
new file mode 100644
index 0000000..dd22183
--- /dev/null
+++ b/nbd_server_v10.py
@@ -0,0 +1,221 @@
+#!/usr/bin/env python3
+"""
+NBD server v10 - PERC H710 corrected chunk translation + merged GDT overlay.
+
+Key fix over v9: all 5 chunks per stripe group contain filesystem data.
+The old formula used a 4-chunk stride between groups, making ~20% of blocks
+unreadable and shifting every address past group 0 by an accumulating error.
+
+Correct formula: phys = LV_START + group*5*CHUNK + chunk_idx*CHUNK + intra
+for ALL chunk_idx values 0-4.
+
+Usage:
+    python3 build_merged_v2.py        # rebuild /tmp/merged_gdt.bin
+    python3 nbd_server_v10.py &
+    nbd-client 127.0.0.1 10809 /dev/nbd0 -N ""
+    mount -o ro /dev/nbd0 /mnt/fs
+"""
+
+import socket, struct, threading, sys, os
+
+DEV           = '/dev/md0'
+MERGED_GDT    = '/tmp/merged_gdt.bin'
+CHUNK_BYTES   = 128 * 512          # 64 KB
+LV_PHYS_START = 5120000 * 512
+VIRT_SIZE     = 9365766144 * 512
+
+BSIZE         = 4096
+GDT_ENTRY_SZ  = 64
+NUM_GROUPS    = 35728
+GDT_VIRT_START = BSIZE
+GDT_VIRT_END   = BSIZE + NUM_GROUPS * GDT_ENTRY_SZ
+
+# NBD protocol constants
+NBDMAGIC            = 0x4e42444d41474943
+IHAVEOPT            = 0x49484156454F5054
+REPLYMAGIC          = 0x3e889045565a9
+NBD_OPT_EXPORT_NAME = 1
+NBD_OPT_ABORT       = 2
+NBD_OPT_LIST        = 3
+NBD_OPT_GO          = 7
+NBD_REP_ACK         = 1
+NBD_REP_SERVER      = 2
+NBD_REP_INFO        = 3
+NBD_REP_ERR_UNSUP   = (1 << 31) | 1
+NBD_INFO_EXPORT     = 0
+NBD_FLAG_HAS_FLAGS  = 1 << 0
+NBD_FLAG_READ_ONLY  = 1 << 1
+NBD_FLAG_SEND_FLUSH = 1 << 2
+NBD_REQUEST_MAGIC   = 0x25609513
+NBD_REPLY_MAGIC     = 0x67446698
+NBD_CMD_READ        = 0
+NBD_CMD_DISC        = 2
+NBD_CMD_FLUSH       = 3
+TX_FLAGS = NBD_FLAG_HAS_FLAGS | NBD_FLAG_READ_ONLY | NBD_FLAG_SEND_FLUSH
+
+# Load merged GDT at startup
+print(f'Loading merged GDT from {MERGED_GDT}...')
+if not os.path.exists(MERGED_GDT):
+    print(f'ERROR: {MERGED_GDT} not found. Run build_merged_v2.py first.')
+    sys.exit(1)
+
+with open(MERGED_GDT, 'rb') as f:
+    MERGED_GDT_DATA = f.read()
+
+expected = NUM_GROUPS * GDT_ENTRY_SZ
+if len(MERGED_GDT_DATA) != expected:
+    print(f'ERROR: merged GDT is {len(MERGED_GDT_DATA)} bytes, expected {expected}')
+    sys.exit(1)
+
+print(f'Merged GDT loaded: {len(MERGED_GDT_DATA)//1024}KB ({NUM_GROUPS} groups)')
+
+
+def raw_read(virt_offset, length):
+    """PERC H710 chunk translation — all 5 chunks per group are filesystem data."""
+    result = bytearray(length)
+    pos = virt_offset
+    remaining = length
+    with open(DEV, 'rb') as f:
+        while remaining > 0:
+            group     = pos // (5 * CHUNK_BYTES)
+            in_group  = pos % (5 * CHUNK_BYTES)
+            chunk_idx = in_group // CHUNK_BYTES
+            intra     = in_group % CHUNK_BYTES
+            seg_len   = min(CHUNK_BYTES - intra, remaining)
+            dst_off   = pos - virt_offset
+            phys = (LV_PHYS_START
+                    + group * 5 * CHUNK_BYTES
+                    + chunk_idx * CHUNK_BYTES
+                    + intra)
+            f.seek(phys)
+            data = f.read(seg_len)
+            result[dst_off:dst_off + len(data)] = data
+            pos       += seg_len
+            remaining -= seg_len
+    return result
+
+
+def read_virtual(virt_offset, length):
+    """Read with merged GDT overlay over the primary GDT region only."""
+    data    = raw_read(virt_offset, length)
+    req_end = virt_offset + length
+
+    if virt_offset < GDT_VIRT_END and req_end > GDT_VIRT_START:
+        ol_start = max(virt_offset, GDT_VIRT_START)
+        ol_end   = min(req_end, GDT_VIRT_END)
+        src_off  = ol_start - GDT_VIRT_START
+        dst_off  = ol_start - virt_offset
+        n        = ol_end - ol_start
+        data[dst_off:dst_off + n] = MERGED_GDT_DATA[src_off:src_off + n]
+
+    return bytes(data)
+
+
+def recv_all(conn, n):
+    buf = b''
+    while len(buf) < n:
+        d = conn.recv(n - len(buf))
+        if not d:
+            raise ConnectionError('disconnected')
+        buf += d
+    return buf
+
+
+def send_reply(conn, opt, rtype, data=b''):
+    conn.sendall(struct.pack('>Q', REPLYMAGIC))
+    conn.sendall(struct.pack('>I', opt))
+    conn.sendall(struct.pack('>I', rtype))
+    conn.sendall(struct.pack('>I', len(data)))
+    if data:
+        conn.sendall(data)
+
+
+def handle_client(conn, addr):
+    print(f'[nbd] {addr} connected')
+    try:
+        conn.sendall(struct.pack('>Q', NBDMAGIC))
+        conn.sendall(struct.pack('>Q', IHAVEOPT))
+        conn.sendall(struct.pack('>H', 0x0003))
+        recv_all(conn, 4)
+
+        while True:
+            hdr = recv_all(conn, 16)
+            _, opt, opt_len = struct.unpack('>QII', hdr)
+            opt_data = recv_all(conn, opt_len) if opt_len else b''
+
+            if opt == NBD_OPT_EXPORT_NAME:
+                conn.sendall(struct.pack('>Q', VIRT_SIZE))
+                conn.sendall(struct.pack('>H', TX_FLAGS))
+                break
+            elif opt == NBD_OPT_GO:
+                info = struct.pack('>HQH', NBD_INFO_EXPORT, VIRT_SIZE, TX_FLAGS)
+                send_reply(conn, opt, NBD_REP_INFO, info)
+                send_reply(conn, opt, NBD_REP_ACK)
+                break
+            elif opt == NBD_OPT_LIST:
+                send_reply(conn, opt, NBD_REP_SERVER, struct.pack('>I', 0))
+                send_reply(conn, opt, NBD_REP_ACK)
+            elif opt == NBD_OPT_ABORT:
+                send_reply(conn, opt, NBD_REP_ACK)
+                return
+            else:
+                send_reply(conn, opt, NBD_REP_ERR_UNSUP)
+
+        print(f'[nbd] {addr} transmission')
+        while True:
+            hdr = recv_all(conn, 28)
+            magic, flags, cmd, handle, offset, length = \
+                struct.unpack('>IHHQQI', hdr)
+            if magic != NBD_REQUEST_MAGIC:
+                return
+
+            if cmd == NBD_CMD_READ:
+                try:
+                    payload = read_virtual(offset, length)
+                except Exception as e:
+                    print(f'[nbd] read error {offset}+{length}: {e}')
+                    payload = b'\x00' * length
+                conn.sendall(struct.pack('>IIQ', NBD_REPLY_MAGIC, 0, handle))
+                conn.sendall(payload)
+            elif cmd == NBD_CMD_FLUSH:
+                conn.sendall(struct.pack('>IIQ', NBD_REPLY_MAGIC, 0, handle))
+            elif cmd == NBD_CMD_DISC:
+                print(f'[nbd] {addr} disconnected')
+                return
+            else:
+                conn.sendall(struct.pack('>IIQ', NBD_REPLY_MAGIC, 1, handle))
+
+    except (ConnectionError, BrokenPipeError, ConnectionResetError):
+        print(f'[nbd] {addr} dropped')
+    except Exception as e:
+        print(f'[nbd] {addr} error: {e}')
+        import traceback; traceback.print_exc()
+    finally:
+        conn.close()
+
+
+def main():
+    print('PERC H710 recovery NBD server v10')
+    print(f'  device     : {DEV}')
+    print(f'  lv_start   : byte {LV_PHYS_START}')
+    print(f'  virt_size  : {VIRT_SIZE // 1024**3} GB')
+    print(f'  GDT region : bytes {GDT_VIRT_START}-{GDT_VIRT_END}')
+    print(f'  translation: group*5*CHUNK (all 5 chunks are filesystem data)')
+    print()
+
+    srv = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    srv.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+    srv.bind(('127.0.0.1', 10809))
+    srv.listen(5)
+    print('Listening on 127.0.0.1:10809')
+    print('  nbd-client 127.0.0.1 10809 /dev/nbd0 -N ""')
+    print()
+
+    while True:
+        conn, addr = srv.accept()
+        threading.Thread(target=handle_client, args=(conn, addr),
+                         daemon=True).start()
+
+
+if __name__ == '__main__':
+    main()
diff --git a/test/nbd_server_v9.py b/nbd_server_v9.py
similarity index 100%
rename from test/nbd_server_v9.py
rename to nbd_server_v9.py