diff --git a/head.go b/head.go
index 07724b965515c3a54779fa79f2abcfd010bbafdc..1b8af29f0cb4b6a5446a3ecede46cc0ae86f6da5 100644
--- a/head.go
+++ b/head.go
@@ -409,6 +409,7 @@ func (h *HeadBlock) updateMapping() {
 	h.mtx.RLock()
 
 	if h.mapper.sortable != nil && h.mapper.Len() == len(h.descs) {
+		h.mtx.RUnlock()
 		return
 	}
 
diff --git a/wal.go b/wal.go
index fc08d7ce9372e13764bc764841da35b349366319..b22906e93ebf3e31520bf24412a847762e911901 100644
--- a/wal.go
+++ b/wal.go
@@ -174,7 +174,7 @@ const (
 	// walPageBytes is the alignment for flushing records to the backing Writer.
 	// It should be a multiple of the minimum sector size so that WAL can safely
 	// distinguish between torn writes and ordinary data corruption.
-	walPageBytes = 32 * minSectorSize
+	walPageBytes = 16 * minSectorSize
 )
 
 func newWALEncoder(f *os.File) (*walEncoder, error) {
diff --git a/writer.go b/writer.go
index f91ca84b35be2ea0105963742d6d2ee86854e11b..c246bad0d70448bc2bc18770c3b61aeade0e0ac8 100644
--- a/writer.go
+++ b/writer.go
@@ -9,6 +9,7 @@ import (
 	"strings"
 
 	"github.com/bradfitz/slice"
+	"github.com/coreos/etcd/pkg/ioutil"
 	"github.com/fabxc/tsdb/chunks"
 	"github.com/fabxc/tsdb/labels"
 	"github.com/pkg/errors"
@@ -22,6 +23,8 @@ const (
 	MagicIndex = 0xBAAAD700
 )
 
+const compactionPageBytes = minSectorSize * 64
+
 // SeriesWriter serializes a time block of chunked series data.
 type SeriesWriter interface {
 	// WriteSeries writes the time series data chunks for a single series.
@@ -40,16 +43,18 @@ type SeriesWriter interface {
 // seriesWriter implements the SeriesWriter interface for the standard
 // serialization format.
 type seriesWriter struct {
-	w io.Writer
-	n int64
-	c int
+	ow io.Writer
+	w  *ioutil.PageWriter
+	n  int64
+	c  int
 
 	index IndexWriter
 }
 
 func newSeriesWriter(w io.Writer, index IndexWriter) *seriesWriter {
 	return &seriesWriter{
-		w:     w,
+		ow:    w,
+		w:     ioutil.NewPageWriter(w, compactionPageBytes, 0),
 		n:     0,
 		index: index,
 	}
@@ -128,7 +133,7 @@ func (w *seriesWriter) Size() int64 {
 }
 
 func (w *seriesWriter) Close() error {
-	return nil
+	return w.w.Flush()
 }
 
 // ChunkMeta holds information about a chunk of data.
@@ -178,8 +183,9 @@ type indexWriterSeries struct {
 // indexWriter implements the IndexWriter interface for the standard
 // serialization format.
 type indexWriter struct {
-	w io.Writer
-	n int64
+	ow io.Writer
+	w  *ioutil.PageWriter
+	n  int64
 
 	series map[uint32]*indexWriterSeries
 
@@ -190,7 +196,8 @@ type indexWriter struct {
 
 func newIndexWriter(w io.Writer) *indexWriter {
 	return &indexWriter{
-		w:       w,
+		w:       ioutil.NewPageWriter(w, compactionPageBytes, 0),
+		ow:      w,
 		n:       0,
 		symbols: make(map[string]uint32, 4096),
 		series:  make(map[uint32]*indexWriterSeries, 4096),
@@ -489,5 +496,8 @@ func (w *indexWriter) finalize() error {
 }
 
 func (w *indexWriter) Close() error {
-	return w.finalize()
+	if err := w.finalize(); err != nil {
+		return err
+	}
+	return w.w.Flush()
 }