diff --git a/chunk/chunk.go b/chunk/chunk.go
index 36efcce..438e355 100644
--- a/chunk/chunk.go
+++ b/chunk/chunk.go
@@ -1,13 +1,23 @@
 package chunk
 
-import "io"
+import (
+	"io"
+
+	"pcloud/api"
+)
+
+type ChunkInfo struct {
+	Status    api.ChunkStatus
+	Size      int
+	Committed int
+}
 
 type Chunk interface {
-	SizeBytes() int
-	ReadSeeker() io.ReadSeeker
-	Writer() io.Writer
+	Stats() (ChunkInfo, error)
+	ReaderAt() io.ReaderAt
+	WriterAt() io.WriterAt
 }
 
 type ChunkFactory interface {
-	New() Chunk
+	New(size int) Chunk
 }
diff --git a/chunk/file.go b/chunk/file.go
new file mode 100644
index 0000000..ddb43f6
--- /dev/null
+++ b/chunk/file.go
@@ -0,0 +1,49 @@
+package chunk
+
+import (
+	"io"
+	"os"
+
+	"pcloud/api"
+)
+
+type ReadOnlyFileChunk struct {
+	f      *os.File
+	offset int
+	size   int
+}
+
+func NewReadOnlyFileChunk(f *os.File, offset, size int) Chunk {
+	return &ReadOnlyFileChunk{f, offset, size}
+}
+
+func (c *ReadOnlyFileChunk) Stats() (ChunkInfo, error) {
+	return ChunkInfo{
+		Status:    api.ChunkStatus_READY,
+		Size:      c.size,
+		Committed: c.size}, nil
+}
+
+func (c *ReadOnlyFileChunk) ReaderAt() io.ReaderAt {
+	return &fileReader{c.f}
+}
+
+func (c *ReadOnlyFileChunk) WriterAt() io.WriterAt {
+	return &fileWriter{c.f}
+}
+
+type fileReader struct {
+	f *os.File
+}
+
+func (f *fileReader) ReadAt(b []byte, offset int64) (int, error) {
+	return f.f.ReadAt(b, offset)
+}
+
+type fileWriter struct {
+	f *os.File
+}
+
+func (f *fileWriter) WriteAt(b []byte, offset int64) (int, error) {
+	return f.f.WriteAt(b, offset)
+}
diff --git a/chunk/in_memory.go b/chunk/in_memory.go
index cd95427..ca7259c 100644
--- a/chunk/in_memory.go
+++ b/chunk/in_memory.go
@@ -2,28 +2,67 @@
 
 import (
 	"bytes"
+	"errors"
 	"io"
+
+	"pcloud/api"
 )
 
 type InMemoryChunk struct {
-	payload bytes.Buffer
+	status    api.ChunkStatus
+	payload   []byte
+	committed int
 }
 
-func (c *InMemoryChunk) SizeBytes() int {
-	return len(c.payload.Bytes())
+func (c *InMemoryChunk) Stats() (ChunkInfo, error) {
+	return ChunkInfo{c.status, len(c.payload), c.committed}, nil
 }
 
-func (c *InMemoryChunk) ReadSeeker() io.ReadSeeker {
-	return bytes.NewReader(c.payload.Bytes())
+func (c *InMemoryChunk) ReaderAt() io.ReaderAt {
+	return bytes.NewReader(c.payload[:c.committed])
 }
 
-func (c *InMemoryChunk) Writer() io.Writer {
-	return &c.payload
+func (c *InMemoryChunk) WriterAt() io.WriterAt {
+	return &byteWriter{c}
+}
+
+type byteWriter struct {
+	c *InMemoryChunk
+}
+
+func (w *byteWriter) WriteAt(p []byte, offset int64) (n int, err error) {
+	if int(offset) > w.c.committed {
+		panic(1)
+		return 0, errors.New("Gaps are not allowed when writing in chunks")
+	}
+	if int(offset) < w.c.committed {
+		if int(offset)+len(p) <= w.c.committed {
+			if bytes.Compare(w.c.payload[int(offset):int(offset)+len(p)], p) != 0 {
+				panic(2)
+				return 0, errors.New("Can not change contents of allready committed chunk bytes")
+			}
+			panic(3)
+			return len(p), nil
+		}
+		n = w.c.committed - int(offset)
+		p = p[n:]
+		offset = int64(w.c.committed)
+	}
+	if w.c.committed+len(p) > len(w.c.payload) {
+		panic(4)
+		return 0, errors.New("In memory chunk does not have enough space available")
+	}
+	n += copy(w.c.payload[w.c.committed:], p)
+	w.c.committed += n
+	return
 }
 
 type InMemoryChunkFactory struct {
 }
 
-func (f InMemoryChunkFactory) New() Chunk {
-	return &InMemoryChunk{}
+func (f InMemoryChunkFactory) New(size int) Chunk {
+	return &InMemoryChunk{
+		status:    api.ChunkStatus_CREATED,
+		payload:   make([]byte, size),
+		committed: 0}
 }
diff --git a/chunk/in_memory_test.go b/chunk/in_memory_test.go
index 7970d14..b9711ca 100644
--- a/chunk/in_memory_test.go
+++ b/chunk/in_memory_test.go
@@ -6,19 +6,19 @@
 )
 
 func TestConcurrentReads(t *testing.T) {
-	c := InMemoryChunkFactory{}.New()
-	if _, err := c.Writer().Write([]byte("abcd")); err != nil {
+	c := InMemoryChunkFactory{}.New(4)
+	if _, err := c.WriterAt().WriteAt([]byte("abcd"), 0); err != nil {
 		panic(err)
 	}
 	d1 := make([]byte, 2)
 	d2 := make([]byte, 3)
-	if _, err := c.ReadSeeker().Read(d1); err != nil {
+	if _, err := c.ReaderAt().ReadAt(d1, 0); err != nil {
 		t.Error(err)
 	}
 	if bytes.Compare(d1, []byte("ab")) != 0 {
 		t.Errorf("Expected: %s\nActual: %s", "ab", d1)
 	}
-	if _, err := c.ReadSeeker().Read(d2); err != nil {
+	if _, err := c.ReaderAt().ReadAt(d2, 0); err != nil {
 		t.Error(err)
 	}
 	if bytes.Compare(d2, []byte("abc")) != 0 {
diff --git a/chunk/remote.go b/chunk/remote.go
index 1cb57f1..0da0ad8 100644
--- a/chunk/remote.go
+++ b/chunk/remote.go
@@ -2,7 +2,6 @@
 
 import (
 	"context"
-	"errors"
 	"io"
 
 	"pcloud/api"
@@ -13,48 +12,63 @@
 	client  api.ChunkStorageClient
 }
 
-func (r *RemoteChunk) SizeBytes() int {
-	return 0
+func (r *RemoteChunk) Stats() (info ChunkInfo, err error) {
+	resp, err := r.client.GetChunkStatus(
+		context.Background(),
+		&api.GetChunkStatusRequest{ChunkId: r.chunkId})
+	if err != nil {
+		return
+	}
+	info = ChunkInfo{
+		resp.Status,
+		int(resp.TotalBytes),
+		int(resp.CommittedBytes)}
+	return
 }
 
-func (r *RemoteChunk) ReadSeeker() io.ReadSeeker {
-	return &remoteChunkReadSeeker{
+func (r *RemoteChunk) ReaderAt() io.ReaderAt {
+	return &remoteChunkReaderAt{
 		chunkId: r.chunkId,
 		client:  r.client}
 }
 
-func (r *RemoteChunk) Writer() io.Writer {
-	return nil
+func (r *RemoteChunk) WriterAt() io.WriterAt {
+	return &remoteChunkWriterAt{
+		chunkId: r.chunkId,
+		client:  r.client}
 }
 
-type remoteChunkReadSeeker struct {
+type remoteChunkReaderAt struct {
 	chunkId string
 	client  api.ChunkStorageClient
-	offset  int64
 }
 
-func (c *remoteChunkReadSeeker) Seek(offset int64, whence int) (int64, error) {
-	if whence != io.SeekStart {
-		return 0, errors.New("Seek: RemoteChunk only supports SeekStart whence")
-	}
-	c.offset = offset
-	return offset, nil
-}
-
-func (c *remoteChunkReadSeeker) Read(p []byte) (n int, err error) {
+func (c *remoteChunkReaderAt) ReadAt(p []byte, offset int64) (n int, err error) {
 	req := api.ReadChunkRequest{
 		ChunkId:  c.chunkId,
-		Offset:   int32(c.offset), // TODO(lekva): must be int64
+		Offset:   int32(offset),
 		NumBytes: int32(len(p))}
 	resp, err := c.client.ReadChunk(context.Background(), &req)
 	if err != nil {
 		return
 	}
 	n = copy(p, resp.Data)
-	c.offset += int64(n)
 	return
 }
 
-type PrimaryReplicaChunk struct {
+type remoteChunkWriterAt struct {
 	chunkId string
+	client  api.ChunkStorageClient
+}
+
+func (c *remoteChunkWriterAt) WriteAt(p []byte, offset int64) (n int, err error) {
+	req := api.WriteChunkRequest{
+		ChunkId: c.chunkId,
+		Offset:  int32(offset),
+		Data:    p}
+	resp, err := c.client.WriteChunk(context.Background(), &req)
+	if resp != nil {
+		n = int(resp.BytesWritten)
+	}
+	return
 }
diff --git a/chunk/replicator.go b/chunk/replicator.go
index 1c77534..fe49862 100644
--- a/chunk/replicator.go
+++ b/chunk/replicator.go
@@ -16,7 +16,13 @@
 
 type NonChangingPrimaryReplicaChangeListener struct {
 	chunkId string
-	address string
+	ch      chan string
+}
+
+func NewNonChangingPrimaryReplicaChangeListener(chunkId, address string) PrimaryReplicaChangeListener {
+	ch := make(chan string, 1)
+	ch <- address
+	return &NonChangingPrimaryReplicaChangeListener{chunkId, ch}
 }
 
 func (l NonChangingPrimaryReplicaChangeListener) ChunkId() string {
@@ -24,48 +30,54 @@
 }
 
 func (l NonChangingPrimaryReplicaChangeListener) Address() <-chan string {
-	ch := make(chan string, 1)
-	ch <- l.address
-	return ch
+	return l.ch
 }
 
-func replicate(ctx context.Context, dst, src Chunk) {
-	inp := src.ReadSeeker()
-	inp.Seek(int64(src.SizeBytes()), io.SeekStart)
-	out := dst.Writer()
+func replicate(ctx context.Context, dst, src Chunk, done chan<- int) {
+	dstInfo, err := dst.Stats()
+	if err != nil {
+		panic(err)
+	}
+	inp := src.ReaderAt()
+	replicated := dstInfo.Committed
+	out := dst.WriterAt()
 	for {
 		select {
 		default:
 			p := make([]byte, 100)
-			n, _ := inp.Read(p)
+			n, err := inp.ReadAt(p, int64(replicated))
 			if n > 0 {
-				out.Write(p[:n])
+				m, _ := out.WriteAt(p[:n], int64(replicated))
+				replicated += m
 			}
+			if err == io.EOF {
+				done <- 1
+				return
+			}
+
 		case <-ctx.Done():
 			return
 		}
 	}
 }
 
-func dialConn(address string) (*grpc.ClientConn, error) {
-	var opts []grpc.DialOption
-	opts = append(opts, grpc.WithInsecure())
-	opts = append(opts, grpc.WithBlock())
-	return grpc.Dial(address, opts...)
-
-}
-
-func replicateFromPrimary(ctx context.Context, dst Chunk, l PrimaryReplicaChangeListener) {
+func ReplicateFromPrimary(ctx context.Context, dst Chunk, l PrimaryReplicaChangeListener) {
+	var done chan int
 	var cancel context.CancelFunc = nil
 	for {
 		select {
+		case <-done:
+			return
 		case <-ctx.Done():
 			return
 		case address := <-l.Address():
 			if cancel != nil {
 				cancel()
 			}
-			conn, err := dialConn(address)
+			var opts []grpc.DialOption
+			opts = append(opts, grpc.WithInsecure())
+			opts = append(opts, grpc.WithBlock())
+			conn, err := grpc.Dial(address, opts...)
 			if err == nil {
 				continue
 			}
@@ -73,7 +85,38 @@
 			src := RemoteChunk{l.ChunkId(), client}
 			replicatorCtx, cancelFn := context.WithCancel(context.Background())
 			cancel = cancelFn
-			go replicate(replicatorCtx, dst, &src)
+			done = make(chan int, 1)
+			go replicate(replicatorCtx, dst, &src, done)
+		}
+	}
+}
+
+func WriteToPrimary(ctx context.Context, src Chunk, l PrimaryReplicaChangeListener) {
+	var done chan int
+	var cancel context.CancelFunc = nil
+	for {
+		select {
+		case <-done:
+			return
+		case <-ctx.Done():
+			return
+		case address := <-l.Address():
+			if cancel != nil {
+				cancel()
+			}
+			var opts []grpc.DialOption
+			opts = append(opts, grpc.WithInsecure())
+			opts = append(opts, grpc.WithBlock())
+			conn, err := grpc.Dial(address, opts...)
+			if err != nil {
+				continue
+			}
+			client := api.NewChunkStorageClient(conn)
+			dst := RemoteChunk{l.ChunkId(), client}
+			replicatorCtx, cancelFn := context.WithCancel(context.Background())
+			cancel = cancelFn
+			done = make(chan int, 1)
+			go replicate(replicatorCtx, &dst, src, done)
 		}
 	}
 }
diff --git a/chunk/server.go b/chunk/server.go
index 2829471..0566c16 100644
--- a/chunk/server.go
+++ b/chunk/server.go
@@ -1,9 +1,9 @@
 package chunk
 
 import (
-	"bytes"
 	"context"
-	"io"
+	"fmt"
+	"log"
 
 	"sync"
 
@@ -16,8 +16,8 @@
 	replicatorCancel sync.Map
 }
 
-func NewChunkServer() *ChunkServer {
-	return &ChunkServer{}
+func NewChunkServer(factory ChunkFactory) *ChunkServer {
+	return &ChunkServer{factory: factory}
 }
 
 func (s *ChunkServer) ListChunks(
@@ -31,56 +31,95 @@
 	return
 }
 
+func (s *ChunkServer) CreateChunk(
+	ctx context.Context,
+	req *api.CreateChunkRequest) (resp *api.CreateChunkResponse, err error) {
+	chunk := s.factory.New(int(req.Size))
+	s.chunks.Store(req.ChunkId, chunk)
+	switch req.Role {
+	case api.ReplicaRole_SECONDARY:
+		ctx, cancel := context.WithCancel(context.Background())
+		s.replicatorCancel.Store(req.ChunkId, cancel)
+		primaryListener := NewNonChangingPrimaryReplicaChangeListener(
+			req.ChunkId,
+			req.PrimaryAddress)
+		go ReplicateFromPrimary(ctx, chunk, primaryListener)
+	case api.ReplicaRole_PRIMARY:
+		{
+		}
+	}
+	resp = &api.CreateChunkResponse{}
+	log.Printf("Created chunk: %s\n", req.ChunkId)
+	return
+
+}
+
+func (s *ChunkServer) GetChunkStatus(
+	ctx context.Context,
+	req *api.GetChunkStatusRequest) (resp *api.GetChunkStatusResponse, err error) {
+	if chunk, ok := s.chunks.Load(req.ChunkId); ok {
+		c := chunk.(Chunk)
+		var info ChunkInfo
+		info, err = c.Stats()
+		if err != nil {
+			return
+		}
+		resp = &api.GetChunkStatusResponse{
+			Status:         info.Status,
+			TotalBytes:     int32(info.Size),
+			CommittedBytes: int32(info.Committed)}
+		return
+	}
+	return nil, fmt.Errorf("Could not fund chunk: %s", req.ChunkId)
+}
+
 func (s *ChunkServer) ReadChunk(
 	ctx context.Context,
 	req *api.ReadChunkRequest) (resp *api.ReadChunkResponse, err error) {
 	if value, ok := s.chunks.Load(req.ChunkId); ok {
 		chunk := value.(Chunk)
-		src := chunk.ReadSeeker()
-		if req.Offset != 0 {
-			_, err = src.Seek(int64(req.Offset), io.SeekStart)
-			if err != nil {
-				return
-			}
+		b := make([]byte, req.NumBytes)
+		var n int
+		n, err = chunk.ReaderAt().ReadAt(b, int64(req.Offset))
+		if n == 0 {
+			return
 		}
-		var dst bytes.Buffer
-		if req.NumBytes != 0 {
-			_, err = io.CopyN(&dst, src, int64(req.NumBytes))
-		} else {
-			_, err = io.Copy(&dst, src)
-		}
-		if err == nil {
-			resp = &api.ReadChunkResponse{Data: dst.Bytes()}
-		}
+		return &api.ReadChunkResponse{Data: b[:n]}, nil
+
+	} else {
+		return nil, fmt.Errorf("Chunk not found: %s", req.ChunkId)
 	}
-	return
+}
+
+func (s *ChunkServer) WriteChunk(
+	ctx context.Context,
+	req *api.WriteChunkRequest) (resp *api.WriteChunkResponse, err error) {
+	if value, ok := s.chunks.Load(req.ChunkId); ok {
+		chunk := value.(Chunk)
+		var n int
+		n, err = chunk.WriterAt().WriteAt(req.Data, int64(req.Offset))
+		if n == 0 {
+			return
+		}
+		return &api.WriteChunkResponse{BytesWritten: int32(n)}, nil
+
+	} else {
+		return nil, fmt.Errorf("Chunk not found: %s", req.ChunkId)
+	}
 }
 
 func (s *ChunkServer) StoreChunk(
 	ctx context.Context,
 	req *api.StoreChunkRequest) (resp *api.StoreChunkResponse, err error) {
-	chunk := s.factory.New()
-	_, err = chunk.Writer().Write(req.Data)
+	chunk := s.factory.New(len(req.Data))
 	s.chunks.Store(req.ChunkId, chunk)
+	_, err = chunk.WriterAt().WriteAt(req.Data, 0)
 	if err == nil {
 		resp = &api.StoreChunkResponse{}
 	}
 	return
 }
 
-func (s *ChunkServer) ReplicateChunk(
-	ctx context.Context,
-	req *api.ReplicateChunkRequest) (resp *api.ReplicateChunkResponse, err error) {
-	chunk := s.factory.New()
-	s.chunks.Store(req.ChunkId, chunk)
-	ctx, cancel := context.WithCancel(context.Background())
-	s.replicatorCancel.Store(req.ChunkId, cancel)
-	go replicateFromPrimary(ctx, chunk, NonChangingPrimaryReplicaChangeListener{req.ChunkId, req.PrimaryChunkServer})
-	resp = &api.ReplicateChunkResponse{}
-	return
-
-}
-
 func (s *ChunkServer) RemoveChunk(
 	ctx context.Context,
 	req *api.RemoveChunkRequest) (resp *api.RemoveChunkResponse, err error) {
diff --git a/chunk/server_test.go b/chunk/server_test.go
index f57a925..70f209f 100644
--- a/chunk/server_test.go
+++ b/chunk/server_test.go
@@ -27,7 +27,8 @@
 		t.Error(err)
 	}
 	resp, err := s.ReadChunk(context.Background(), &api.ReadChunkRequest{
-		ChunkId: "foo"})
+		ChunkId:  "foo",
+		NumBytes: 100})
 	if err != nil {
 		t.Error(err)
 	}
@@ -65,8 +66,9 @@
 		t.Errorf("Expected: %s\nGot: %s\n", "ll", resp.Data)
 	}
 	resp, err = s.ReadChunk(context.Background(), &api.ReadChunkRequest{
-		ChunkId: "foo",
-		Offset:  4})
+		ChunkId:  "foo",
+		Offset:   4,
+		NumBytes: 100})
 	if err != nil {
 		t.Error(err)
 	}