diff --git a/block.go b/block.go
index 733b1bd6b..bc9f581ab 100644
--- a/block.go
+++ b/block.go
@@ -113,7 +113,7 @@ type BlockStats struct {
 type BlockMetaCompaction struct {
 	// Maximum number of compaction cycles any source block has
 	// gone through.
-	Generation int `json:"generation"`
+	Level int `json:"level"`
 	// ULIDs of all source head blocks that went into the block.
 	Sources []ulid.ULID `json:"sources,omitempty"`
 }
diff --git a/chunks/chunk.go b/chunks/chunk.go
index 21b00b3eb..181693fae 100644
--- a/chunks/chunk.go
+++ b/chunks/chunk.go
@@ -104,6 +104,9 @@ func (p *pool) Put(c Chunk) error {
 	switch c.Encoding() {
 	case EncXOR:
 		xc, ok := c.(*XORChunk)
+		// This may happen often with wrapped chunks. Nothing we can really do about
+		// it but returning an error would cause a lot of allocations again. Thus,
+		// we just skip it.
 		if !ok {
 			return nil
 		}
diff --git a/compact.go b/compact.go
index 5d2e4c4ce..3860509d8 100644
--- a/compact.go
+++ b/compact.go
@@ -48,22 +48,22 @@ type Compactor interface {
 	// Plan returns a set of non-overlapping directories that can
 	// be compacted concurrently.
 	// Results returned when compactions are in progress are undefined.
-	Plan() ([][]string, error)
+	Plan(dir string) ([]string, error)
 
 	// Write persists a Block into a directory.
-	Write(b Block) error
+	Write(dest string, b Block) error
 
 	// Compact runs compaction against the provided directories. Must
 	// only be called concurrently with results of Plan().
-	Compact(dirs ...string) error
+	Compact(dest string, dirs ...string) error
 }
 
-// compactor implements the Compactor interface.
-type compactor struct {
+// LeveledCompactor implements the Compactor interface.
+type LeveledCompactor struct {
 	dir     string
 	metrics *compactorMetrics
 	logger  log.Logger
-	opts    *compactorOptions
+	opts    *LeveledCompactorOptions
 }
 
 type compactorMetrics struct {
@@ -98,19 +98,18 @@ func newCompactorMetrics(r prometheus.Registerer) *compactorMetrics {
 	return m
 }
 
-type compactorOptions struct {
+type LeveledCompactorOptions struct {
 	blockRanges []int64
 	chunkPool   chunks.Pool
 }
 
-func NewCompactor(dir string, r prometheus.Registerer, l log.Logger, opts *compactorOptions) *compactor {
+func NewLeveledCompactor(r prometheus.Registerer, l log.Logger, opts *LeveledCompactorOptions) *LeveledCompactor {
 	if opts == nil {
-		opts = &compactorOptions{
+		opts = &LeveledCompactorOptions{
 			chunkPool: chunks.NewPool(),
 		}
 	}
-	return &compactor{
-		dir:     dir,
+	return &LeveledCompactor{
 		opts:    opts,
 		logger:  l,
 		metrics: newCompactorMetrics(r),
@@ -130,8 +129,9 @@ type dirMeta struct {
 	meta *BlockMeta
 }
 
-func (c *compactor) Plan() ([][]string, error) {
-	dirs, err := blockDirs(c.dir)
+// Plan returns a list of compactable blocks in the provided directory.
+func (c *LeveledCompactor) Plan(dir string) ([]string, error) {
+	dirs, err := blockDirs(dir)
 	if err != nil {
 		return nil, err
 	}
@@ -143,7 +143,7 @@ func (c *compactor) Plan() ([][]string, error) {
 		if err != nil {
 			return nil, err
 		}
-		if meta.Compaction.Generation > 0 {
+		if meta.Compaction.Level > 0 {
 			dms = append(dms, dirMeta{dir, meta})
 		}
 	}
@@ -155,20 +155,12 @@ func (c *compactor) Plan() ([][]string, error) {
 		return nil, nil
 	}
 
-	sliceDirs := func(dms []dirMeta) [][]string {
-		if len(dms) == 0 {
-			return nil
-		}
-		var res []string
-		for _, dm := range dms {
-			res = append(res, dm.dir)
-		}
-		return [][]string{res}
+	var res []string
+	for _, dm := range c.selectDirs(dms) {
+		res = append(res, dm.dir)
 	}
-
-	planDirs := sliceDirs(c.selectDirs(dms))
-	if len(dirs) > 1 {
-		return planDirs, nil
+	if len(res) > 0 {
+		return res, nil
 	}
 
 	// Compact any blocks that have >5% tombstones.
@@ -179,7 +171,7 @@ func (c *compactor) Plan() ([][]string, error) {
 		}
 
 		if meta.Stats.NumSeries/meta.Stats.NumTombstones <= 20 { // 5%
-			return [][]string{{dms[i].dir}}, nil
+			return []string{dms[i].dir}, nil
 		}
 	}
 
@@ -188,7 +180,7 @@ func (c *compactor) Plan() ([][]string, error) {
 
 // selectDirs returns the dir metas that should be compacted into a single new block.
 // If only a single block range is configured, the result is always nil.
-func (c *compactor) selectDirs(ds []dirMeta) []dirMeta {
+func (c *LeveledCompactor) selectDirs(ds []dirMeta) []dirMeta {
 	if len(c.opts.blockRanges) < 2 || len(ds) < 1 {
 		return nil
 	}
@@ -267,18 +259,18 @@ func compactBlockMetas(blocks ...BlockMeta) (res BlockMeta) {
 	sources := map[ulid.ULID]struct{}{}
 
 	for _, b := range blocks {
-		if b.Compaction.Generation > res.Compaction.Generation {
-			res.Compaction.Generation = b.Compaction.Generation
+		if b.Compaction.Level > res.Compaction.Level {
+			res.Compaction.Level = b.Compaction.Level
 		}
 		for _, s := range b.Compaction.Sources {
 			sources[s] = struct{}{}
 		}
 		// If it's an in memory block, its ULID goes into the sources.
-		if b.Compaction.Generation == 0 {
+		if b.Compaction.Level == 0 {
 			sources[b.ULID] = struct{}{}
 		}
 	}
-	res.Compaction.Generation++
+	res.Compaction.Level++
 
 	for s := range sources {
 		res.Compaction.Sources = append(res.Compaction.Sources, s)
@@ -290,7 +282,9 @@ func compactBlockMetas(blocks ...BlockMeta) (res BlockMeta) {
 	return res
 }
 
-func (c *compactor) Compact(dirs ...string) (err error) {
+// Compact creates a new block in the compactor's directory from the blocks in the
+// provided directories.
+func (c *LeveledCompactor) Compact(dest string, dirs ...string) (err error) {
 	var blocks []Block
 
 	for _, d := range dirs {
@@ -306,24 +300,24 @@ func (c *compactor) Compact(dirs ...string) (err error) {
 	entropy := rand.New(rand.NewSource(time.Now().UnixNano()))
 	uid := ulid.MustNew(ulid.Now(), entropy)
 
-	return c.write(uid, blocks...)
+	return c.write(dest, uid, blocks...)
 }
 
-func (c *compactor) Write(b Block) error {
+func (c *LeveledCompactor) Write(dest string, b Block) error {
 	// Buffering blocks might have been created that often have no data.
 	if b.Meta().Stats.NumSeries == 0 {
-		return errors.Wrap(os.RemoveAll(b.Dir()), "remove empty block")
+		return nil
 	}
 
 	entropy := rand.New(rand.NewSource(time.Now().UnixNano()))
 	uid := ulid.MustNew(ulid.Now(), entropy)
 
-	return c.write(uid, b)
+	return c.write(dest, uid, b)
 }
 
 // write creates a new block that is the union of the provided blocks into dir.
 // It cleans up all files of the old blocks after completing successfully.
-func (c *compactor) write(uid ulid.ULID, blocks ...Block) (err error) {
+func (c *LeveledCompactor) write(dest string, uid ulid.ULID, blocks ...Block) (err error) {
 	c.logger.Log("msg", "compact blocks", "blocks", fmt.Sprintf("%v", blocks))
 
 	defer func(t time.Time) {
@@ -334,7 +328,7 @@ func (c *compactor) write(uid ulid.ULID, blocks ...Block) (err error) {
 		c.metrics.duration.Observe(time.Since(t).Seconds())
 	}(time.Now())
 
-	dir := filepath.Join(c.dir, uid.String())
+	dir := filepath.Join(dest, uid.String())
 	tmp := dir + ".tmp"
 
 	if err = os.RemoveAll(tmp); err != nil {
@@ -382,11 +376,6 @@ func (c *compactor) write(uid ulid.ULID, blocks ...Block) (err error) {
 	if err := renameFile(tmp, dir); err != nil {
 		return errors.Wrap(err, "rename block dir")
 	}
-	for _, b := range blocks {
-		if err := os.RemoveAll(b.Dir()); err != nil {
-			return err
-		}
-	}
 	// Properly sync parent dir to ensure changes are visible.
 	df, err := fileutil.OpenDir(dir)
 	if err != nil {
@@ -403,7 +392,7 @@ func (c *compactor) write(uid ulid.ULID, blocks ...Block) (err error) {
 
 // populateBlock fills the index and chunk writers with new data gathered as the union
 // of the provided blocks. It returns meta information for the new block.
-func (c *compactor) populateBlock(blocks []Block, indexw IndexWriter, chunkw ChunkWriter) (*BlockMeta, error) {
+func (c *LeveledCompactor) populateBlock(blocks []Block, indexw IndexWriter, chunkw ChunkWriter) (*BlockMeta, error) {
 	var (
 		set        compactionSet
 		metas      []BlockMeta
diff --git a/compact_test.go b/compact_test.go
index 91a2812ca..d9791a080 100644
--- a/compact_test.go
+++ b/compact_test.go
@@ -19,8 +19,8 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
-func TestCompactionSelect(t *testing.T) {
-	opts := &compactorOptions{
+func TestLeveledCompactor_Select(t *testing.T) {
+	opts := &LeveledCompactorOptions{
 		blockRanges: []int64{
 			20,
 			60,
@@ -173,7 +173,7 @@ func TestCompactionSelect(t *testing.T) {
 		},
 	}
 
-	c := &compactor{
+	c := &LeveledCompactor{
 		opts: opts,
 	}
 	sliceDirs := func(dms []dirMeta) [][]string {
diff --git a/db.go b/db.go
index fe48b3ce1..8d581cdfa 100644
--- a/db.go
+++ b/db.go
@@ -224,7 +224,7 @@ func Open(dir string, l log.Logger, r prometheus.Registerer, opts *Options) (db
 		db.lockf = &lockf
 	}
 
-	copts := &compactorOptions{
+	copts := &LeveledCompactorOptions{
 		blockRanges: opts.BlockRanges,
 		chunkPool:   db.chunkPool,
 	}
@@ -242,7 +242,7 @@ func Open(dir string, l log.Logger, r prometheus.Registerer, opts *Options) (db
 		copts.blockRanges = copts.blockRanges[:len(copts.blockRanges)-1]
 	}
 
-	db.compactor = NewCompactor(dir, r, l, copts)
+	db.compactor = NewLeveledCompactor(r, l, copts)
 
 	if err := db.reloadBlocks(); err != nil {
 		return nil, err
@@ -390,20 +390,24 @@ func (db *DB) compact() (changes bool, err error) {
 		default:
 		}
 
-		if err = db.compactor.Write(h); err != nil {
+		if err = db.compactor.Write(db.dir, h); err != nil {
 			return changes, errors.Wrap(err, "persist head block")
 		}
 		changes = true
+
+		if err := os.RemoveAll(h.Dir()); err != nil {
+			return changes, errors.Wrap(err, "delete compacted head block")
+		}
 		runtime.GC()
 	}
 
 	// Check for compactions of multiple blocks.
 	for {
-		plans, err := db.compactor.Plan()
+		plan, err := db.compactor.Plan(db.dir)
 		if err != nil {
 			return changes, errors.Wrap(err, "plan compaction")
 		}
-		if len(plans) == 0 {
+		if len(plan) == 0 {
 			break
 		}
 
@@ -413,17 +417,17 @@ func (db *DB) compact() (changes bool, err error) {
 		default:
 		}
 
-		// We just execute compactions sequentially to not cause too extreme
-		// CPU and memory spikes.
-		// TODO(fabxc): return more descriptive plans in the future that allow
-		// estimation of resource usage and conditional parallelization?
-		for _, p := range plans {
-			if err := db.compactor.Compact(p...); err != nil {
-				return changes, errors.Wrapf(err, "compact %s", p)
-			}
-			changes = true
-			runtime.GC()
+		if err := db.compactor.Compact(db.dir, plan...); err != nil {
+			return changes, errors.Wrapf(err, "compact %s", plan)
 		}
+		changes = true
+
+		for _, pd := range plan {
+			if err := os.RemoveAll(pd); err != nil {
+				return changes, errors.Wrap(err, "delete compacted block")
+			}
+		}
+		runtime.GC()
 	}
 
 	return changes, nil
@@ -509,7 +513,7 @@ func (db *DB) reloadBlocks() (err error) {
 
 		b, ok := db.getBlock(meta.ULID)
 		if !ok {
-			if meta.Compaction.Generation == 0 {
+			if meta.Compaction.Level == 0 {
 				b, err = db.openHeadBlock(dir)
 			} else {
 				b, err = newPersistedBlock(dir, db.chunkPool)
@@ -538,7 +542,7 @@ func (db *DB) reloadBlocks() (err error) {
 	db.heads = nil
 
 	for _, b := range blocks {
-		if b.Meta().Compaction.Generation == 0 {
+		if b.Meta().Compaction.Level == 0 {
 			db.heads = append(db.heads, b.(*HeadBlock))
 		}
 	}
@@ -607,6 +611,9 @@ func (db *DB) EnableCompactions() {
 
 // Snapshot writes the current data to the directory.
 func (db *DB) Snapshot(dir string) error {
+	if dir == db.dir {
+		return errors.Errorf("cannot snapshot into base directory")
+	}
 	db.cmtx.Lock()
 	defer db.cmtx.Unlock()
 
@@ -873,7 +880,7 @@ func (db *DB) openHeadBlock(dir string) (*HeadBlock, error) {
 		return nil, errors.Wrap(err, "open WAL %s")
 	}
 
-	h, err := OpenHeadBlock(dir, log.With(db.logger, "block", dir), wal)
+	h, err := OpenHeadBlock(dir, log.With(db.logger, "block", dir), wal, db.compactor)
 	if err != nil {
 		return nil, errors.Wrapf(err, "open head block %s", dir)
 	}
diff --git a/head.go b/head.go
index fae0937ec..045378d9c 100644
--- a/head.go
+++ b/head.go
@@ -52,9 +52,10 @@ var (
 
 // HeadBlock handles reads and writes of time series data within a time window.
 type HeadBlock struct {
-	mtx sync.RWMutex
-	dir string
-	wal WAL
+	mtx       sync.RWMutex
+	dir       string
+	wal       WAL
+	compactor Compactor
 
 	activeWriters uint64
 	highTimestamp int64
@@ -106,7 +107,7 @@ func TouchHeadBlock(dir string, mint, maxt int64) (string, error) {
 }
 
 // OpenHeadBlock opens the head block in dir.
-func OpenHeadBlock(dir string, l log.Logger, wal WAL) (*HeadBlock, error) {
+func OpenHeadBlock(dir string, l log.Logger, wal WAL, c Compactor) (*HeadBlock, error) {
 	meta, err := readMetaFile(dir)
 	if err != nil {
 		return nil, err
@@ -115,6 +116,7 @@ func OpenHeadBlock(dir string, l log.Logger, wal WAL) (*HeadBlock, error) {
 	h := &HeadBlock{
 		dir:        dir,
 		wal:        wal,
+		compactor:  c,
 		series:     []*memSeries{nil}, // 0 is not a valid posting, filled with nil.
 		hashes:     map[uint64][]*memSeries{},
 		values:     map[string]stringset{},
@@ -266,68 +268,14 @@ Outer:
 }
 
 // Snapshot persists the current state of the headblock to the given directory.
-// TODO(gouthamve): Snapshot must be called when there are no active appenders.
-// This has been ensured by acquiring a Lock on DB.mtx, but this limitation should
-// be removed in the future.
+// Callers must ensure that there are no active appenders against the block.
+// DB does this by acquiring its own write lock.
 func (h *HeadBlock) Snapshot(snapshotDir string) error {
-	// if h.meta.Stats.NumSeries == 0 {
-	// 	return nil
-	// }
+	if h.meta.Stats.NumSeries == 0 {
+		return nil
+	}
 
-	// entropy := rand.New(rand.NewSource(time.Now().UnixNano()))
-	// uid := ulid.MustNew(ulid.Now(), entropy)
-
-	// dir := filepath.Join(snapshotDir, uid.String())
-	// tmp := dir + ".tmp"
-
-	// if err := os.RemoveAll(tmp); err != nil {
-	// 	return err
-	// }
-
-	// if err := os.MkdirAll(tmp, 0777); err != nil {
-	// 	return err
-	// }
-
-	// // Populate chunk and index files into temporary directory with
-	// // data of all blocks.
-	// chunkw, err := newChunkWriter(chunkDir(tmp))
-	// if err != nil {
-	// 	return errors.Wrap(err, "open chunk writer")
-	// }
-	// indexw, err := newIndexWriter(tmp)
-	// if err != nil {
-	// 	return errors.Wrap(err, "open index writer")
-	// }
-
-	// meta, err := h.compactor.populateBlock([]Block{h}, indexw, chunkw, nil)
-	// if err != nil {
-	// 	return errors.Wrap(err, "write snapshot")
-	// }
-	// meta.ULID = uid
-	// meta.MaxTime = h.highTimestamp
-
-	// if err = writeMetaFile(tmp, meta); err != nil {
-	// 	return errors.Wrap(err, "write merged meta")
-	// }
-
-	// if err = chunkw.Close(); err != nil {
-	// 	return errors.Wrap(err, "close chunk writer")
-	// }
-	// if err = indexw.Close(); err != nil {
-	// 	return errors.Wrap(err, "close index writer")
-	// }
-
-	// // Create an empty tombstones file.
-	// if err := writeTombstoneFile(tmp, newEmptyTombstoneReader()); err != nil {
-	// 	return errors.Wrap(err, "write new tombstones file")
-	// }
-
-	// // Block successfully written, make visible
-	// if err := renameFile(tmp, dir); err != nil {
-	// 	return errors.Wrap(err, "rename block dir")
-	// }
-
-	return nil
+	return h.compactor.Write(snapshotDir, h)
 }
 
 // Dir returns the directory of the block.
diff --git a/head_test.go b/head_test.go
index c86c40768..eee730774 100644
--- a/head_test.go
+++ b/head_test.go
@@ -43,7 +43,7 @@ func openTestHeadBlock(t testing.TB, dir string) *HeadBlock {
 	wal, err := OpenSegmentWAL(dir, nil, 5*time.Second)
 	require.NoError(t, err)
 
-	h, err := OpenHeadBlock(dir, nil, wal)
+	h, err := OpenHeadBlock(dir, nil, wal, nil)
 	require.NoError(t, err)
 	return h
 }