diff --git a/wal.go b/wal.go
index a930252483..33793d782f 100644
--- a/wal.go
+++ b/wal.go
@@ -3,6 +3,7 @@ package tsdb
 import (
 	"bufio"
 	"encoding/binary"
+	"hash"
 	"hash/crc32"
 	"io"
 	"math"
@@ -47,8 +48,9 @@ type WAL struct {
 	flushInterval time.Duration
 	segmentSize   int64
 
-	cur  *bufio.Writer
-	curN int64
+	crc32 hash.Hash32
+	cur   *bufio.Writer
+	curN  int64
 
 	stopc chan struct{}
 	donec chan struct{}
@@ -79,6 +81,7 @@ func OpenWAL(dir string, l log.Logger, flushInterval time.Duration) (*WAL, error
 		donec:         make(chan struct{}),
 		stopc:         make(chan struct{}),
 		segmentSize:   walSegmentSizeBytes,
+		crc32:         crc32.New(crc32.MakeTable(crc32.Castagnoli)),
 	}
 	if err := w.initSegments(); err != nil {
 		return nil, err
@@ -96,7 +99,7 @@ func (w *WAL) Reader() *WALReader {
 	for _, f := range w.files {
 		rs = append(rs, f)
 	}
-	return &WALReader{rs: rs}
+	return NewWALReader(rs...)
 }
 
 // Log writes a batch of new series labels and samples to the log.
@@ -301,8 +304,8 @@ func (w *WAL) entry(et WALEntryType, flag byte, buf []byte) error {
 		}
 	}
 
-	h := crc32.NewIEEE()
-	wr := io.MultiWriter(h, w.cur)
+	w.crc32.Reset()
+	wr := io.MultiWriter(w.crc32, w.cur)
 
 	b := make([]byte, 6)
 	b[0] = byte(et)
@@ -316,7 +319,7 @@ func (w *WAL) entry(et WALEntryType, flag byte, buf []byte) error {
 	if _, err := wr.Write(buf); err != nil {
 		return err
 	}
-	if _, err := w.cur.Write(h.Sum(nil)); err != nil {
+	if _, err := w.cur.Write(w.crc32.Sum(nil)); err != nil {
 		return err
 	}
 
@@ -407,9 +410,10 @@ func (w *WAL) encodeSamples(samples []refdSample) error {
 
 // WALReader decodes and emits write ahead log entries.
 type WALReader struct {
-	rs  []io.ReadCloser
-	cur int
-	buf []byte
+	rs    []io.ReadCloser
+	cur   int
+	buf   []byte
+	crc32 hash.Hash32
 
 	err     error
 	labels  []labels.Labels
@@ -419,8 +423,9 @@ type WALReader struct {
 // NewWALReader returns a new WALReader over the sequence of the given ReadClosers.
 func NewWALReader(rs ...io.ReadCloser) *WALReader {
 	return &WALReader{
-		rs:  rs,
-		buf: make([]byte, 0, 1024*1024),
+		rs:    rs,
+		buf:   make([]byte, 0, 128*4096),
+		crc32: crc32.New(crc32.MakeTable(crc32.Castagnoli)),
 	}
 }
 
@@ -483,8 +488,8 @@ func (r *WALReader) Next() bool {
 }
 
 func (r *WALReader) entry(cr io.Reader) (WALEntryType, byte, []byte, error) {
-	cw := crc32.NewIEEE()
-	tr := io.TeeReader(cr, cw)
+	r.crc32.Reset()
+	tr := io.TeeReader(cr, r.crc32)
 
 	b := make([]byte, 6)
 	if _, err := tr.Read(b); err != nil {
@@ -513,7 +518,7 @@ func (r *WALReader) entry(cr io.Reader) (WALEntryType, byte, []byte, error) {
 	if err != nil {
 		return 0, 0, nil, err
 	}
-	if exp, has := binary.BigEndian.Uint32(b[:4]), cw.Sum32(); has != exp {
+	if exp, has := binary.BigEndian.Uint32(b[:4]), r.crc32.Sum32(); has != exp {
 		return 0, 0, nil, errors.Errorf("unexpected CRC32 checksum %x, want %x", has, exp)
 	}
 
diff --git a/writer.go b/writer.go
index a73f2bd116..86bb75274e 100644
--- a/writer.go
+++ b/writer.go
@@ -3,6 +3,7 @@ package tsdb
 import (
 	"bufio"
 	"encoding/binary"
+	"hash"
 	"hash/crc32"
 	"io"
 	"sort"
@@ -42,10 +43,11 @@ type SeriesWriter interface {
 // seriesWriter implements the SeriesWriter interface for the standard
 // serialization format.
 type seriesWriter struct {
-	ow io.Writer
-	w  *bufio.Writer
-	n  int64
-	c  int
+	ow    io.Writer
+	w     *bufio.Writer
+	n     int64
+	c     int
+	crc32 hash.Hash
 
 	index IndexWriter
 }
@@ -55,6 +57,7 @@ func newSeriesWriter(w io.Writer, index IndexWriter) *seriesWriter {
 		ow:    w,
 		w:     bufio.NewWriterSize(w, 1*1024*1024),
 		n:     0,
+		crc32: crc32.New(crc32.MakeTable(crc32.Castagnoli)),
 		index: index,
 	}
 }
@@ -82,9 +85,8 @@ func (w *seriesWriter) WriteSeries(ref uint32, lset labels.Labels, chks []ChunkM
 		}
 	}
 
-	// TODO(fabxc): is crc32 enough for chunks of one series?
-	h := crc32.NewIEEE()
-	wr := io.MultiWriter(h, w.w)
+	w.crc32.Reset()
+	wr := io.MultiWriter(w.crc32, w.w)
 
 	// For normal reads we don't need the number of the chunk section but
 	// it allows us to verify checksums without reading the index file.
@@ -117,7 +119,7 @@ func (w *seriesWriter) WriteSeries(ref uint32, lset labels.Labels, chks []ChunkM
 		chk.Chunk = nil
 	}
 
-	if err := w.write(w.w, h.Sum(nil)); err != nil {
+	if err := w.write(w.w, w.crc32.Sum(nil)); err != nil {
 		return err
 	}
 
@@ -195,6 +197,8 @@ type indexWriter struct {
 	symbols      map[string]uint32 // symbol offsets
 	labelIndexes []hashEntry       // label index offsets
 	postings     []hashEntry       // postings lists offsets
+
+	crc32 hash.Hash
 }
 
 func newIndexWriter(w io.Writer) *indexWriter {
@@ -204,6 +208,7 @@ func newIndexWriter(w io.Writer) *indexWriter {
 		n:       0,
 		symbols: make(map[string]uint32, 4096),
 		series:  make(map[uint32]*indexWriterSeries, 4096),
+		crc32:   crc32.New(crc32.MakeTable(crc32.Castagnoli)),
 	}
 }
 
@@ -215,8 +220,8 @@ func (w *indexWriter) write(wr io.Writer, b []byte) error {
 
 // section writes a CRC32 checksummed section of length l and guarded by flag.
 func (w *indexWriter) section(l uint32, flag byte, f func(w io.Writer) error) error {
-	h := crc32.NewIEEE()
-	wr := io.MultiWriter(h, w.w)
+	w.crc32.Reset()
+	wr := io.MultiWriter(w.crc32, w.w)
 
 	b := [5]byte{flag, 0, 0, 0, 0}
 	binary.BigEndian.PutUint32(b[1:], l)
@@ -228,7 +233,7 @@ func (w *indexWriter) section(l uint32, flag byte, f func(w io.Writer) error) er
 	if err := f(wr); err != nil {
 		return errors.Wrap(err, "contents write func")
 	}
-	if err := w.write(w.w, h.Sum(nil)); err != nil {
+	if err := w.write(w.w, w.crc32.Sum(nil)); err != nil {
 		return errors.Wrap(err, "writing checksum")
 	}
 	return nil