diff --git a/archiver.go b/archiver.go
index c181711d7..a26dc3e7f 100644
--- a/archiver.go
+++ b/archiver.go
@@ -9,6 +9,7 @@ import (
 	"path/filepath"
 	"sort"
 	"sync"
+	"time"
 
 	"github.com/restic/chunker"
 	"github.com/restic/restic/backend"
@@ -540,6 +541,30 @@ func (j archiveJob) Copy() pipe.Job {
 	return j.new
 }
 
+const saveIndexTime = 30 * time.Second
+
+// saveIndexes regularly queries the master index for full indexes and saves them.
+func (arch *Archiver) saveIndexes(wg *sync.WaitGroup, done <-chan struct{}) {
+	defer wg.Done()
+
+	ticker := time.NewTicker(saveIndexTime)
+	defer ticker.Stop()
+
+	for {
+		select {
+		case <-done:
+			return
+		case <-ticker.C:
+			debug.Log("Archiver.saveIndexes", "saving full indexes")
+			err := arch.repo.SaveFullIndex()
+			if err != nil {
+				debug.Log("Archiver.saveIndexes", "save indexes returned an error: %v", err)
+				fmt.Fprintf(os.Stderr, "error saving preliminary index: %v\n", err)
+			}
+		}
+	}
+}
+
 // Snapshot creates a snapshot of the given paths. If parentID is set, this is
 // used to compare the files to the ones archived at the time this snapshot was
 // taken.
@@ -623,10 +648,20 @@ func (arch *Archiver) Snapshot(p *Progress, paths []string, parentID *backend.ID
 		go arch.dirWorker(&wg, p, done, dirCh)
 	}
 
+	// run index saver
+	var wgIndexSaver sync.WaitGroup
+	stopIndexSaver := make(chan struct{})
+	wgIndexSaver.Add(1)
+	go arch.saveIndexes(&wgIndexSaver, stopIndexSaver)
+
 	// wait for all workers to terminate
 	debug.Log("Archiver.Snapshot", "wait for workers")
 	wg.Wait()
 
+	// stop index saver
+	close(stopIndexSaver)
+	wgIndexSaver.Wait()
+
 	debug.Log("Archiver.Snapshot", "workers terminated")
 
 	// receive the top-level tree
@@ -681,7 +716,6 @@ func Scan(dirs []string, filter pipe.SelectFunc, p *Progress) (Stat, error) {
 	for _, dir := range dirs {
 		debug.Log("Scan", "Start for %v", dir)
 		err := filepath.Walk(dir, func(str string, fi os.FileInfo, err error) error {
-			debug.Log("Scan.Walk", "%v, fi: %v, err: %v", str, fi, err)
 			// TODO: integrate error reporting
 			if err != nil {
 				fmt.Fprintf(os.Stderr, "error for %v: %v\n", str, err)
diff --git a/repository/index.go b/repository/index.go
index 6107d8c84..006944fb6 100644
--- a/repository/index.go
+++ b/repository/index.go
@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"io"
 	"sync"
+	"time"
 
 	"github.com/restic/restic/backend"
 	"github.com/restic/restic/crypto"
@@ -20,6 +21,7 @@ type Index struct {
 
 	final      bool // set to true for all indexes read from the backend ("finalized")
 	supersedes backend.IDs
+	created    time.Time
 }
 
 type indexEntry struct {
@@ -32,7 +34,8 @@ type indexEntry struct {
 // NewIndex returns a new index.
 func NewIndex() *Index {
 	return &Index{
-		pack: make(map[backend.ID]indexEntry),
+		pack:    make(map[backend.ID]indexEntry),
+		created: time.Now(),
 	}
 }
 
@@ -54,6 +57,42 @@ func (idx *Index) Final() bool {
 	return idx.final
 }
 
+const (
+	indexMinBlobs = 20
+	indexMaxBlobs = 2000
+	indexMinAge   = 2 * time.Minute
+	indexMaxAge   = 15 * time.Minute
+)
+
+// Full returns true iff the index is "full enough" to be saved as a preliminary index.
+func (idx *Index) Full() bool {
+	idx.m.Lock()
+	defer idx.m.Unlock()
+
+	debug.Log("Index.Full", "checking whether index %p is full", idx)
+
+	packs := len(idx.pack)
+	age := time.Now().Sub(idx.created)
+
+	if age > indexMaxAge {
+		debug.Log("Index.Full", "index %p is old enough", idx, age)
+		return true
+	}
+
+	if packs < indexMinBlobs || age < indexMinAge {
+		debug.Log("Index.Full", "index %p only has %d packs or is too young (%v)", idx, packs, age)
+		return false
+	}
+
+	if packs > indexMaxBlobs {
+		debug.Log("Index.Full", "index %p has %d packs", idx, packs)
+		return true
+	}
+
+	debug.Log("Index.Full", "index %p is not full", idx)
+	return false
+}
+
 // Store remembers the id and pack in the index. An existing entry will be
 // silently overwritten.
 func (idx *Index) Store(t pack.BlobType, id backend.ID, pack *backend.ID, offset, length uint) {
diff --git a/repository/master_index.go b/repository/master_index.go
index c032152cc..f7cdae261 100644
--- a/repository/master_index.go
+++ b/repository/master_index.go
@@ -187,7 +187,33 @@ func (mi *MasterIndex) NotFinalIndexes() []*Index {
 		}
 	}
 
-	debug.Log("MasterIndex.NotFinalIndexes", "saving %d indexes", len(list))
+	debug.Log("MasterIndex.NotFinalIndexes", "return %d indexes", len(list))
+	return list
+}
+
+// FullIndexes returns all indexes that are full.
+func (mi *MasterIndex) FullIndexes() []*Index {
+	mi.idxMutex.Lock()
+	defer mi.idxMutex.Unlock()
+
+	var list []*Index
+
+	debug.Log("MasterIndex.FullIndexes", "checking %d indexes", len(mi.idx))
+	for _, idx := range mi.idx {
+		if idx.Final() {
+			debug.Log("MasterIndex.FullIndexes", "index %p is final", idx)
+			continue
+		}
+
+		if idx.Full() {
+			debug.Log("MasterIndex.FullIndexes", "index %p is full", idx)
+			list = append(list, idx)
+		} else {
+			debug.Log("MasterIndex.FullIndexes", "index %p not full", idx)
+		}
+	}
+
+	debug.Log("MasterIndex.FullIndexes", "return %d indexes", len(list))
 	return list
 }
 
diff --git a/repository/repository.go b/repository/repository.go
index 2fe65a963..ac2b8b03b 100644
--- a/repository/repository.go
+++ b/repository/repository.go
@@ -235,7 +235,7 @@ func (r *Repository) findPacker(size uint) (*pack.Packer, error) {
 	if err != nil {
 		return nil, err
 	}
-	debug.Log("Repo.findPacker", "create new pack %p", blob)
+	debug.Log("Repo.findPacker", "create new pack %p for %d bytes", blob, size)
 	return pack.NewPacker(r.key, blob), nil
 }
 
@@ -513,9 +513,9 @@ func (bw *BlobWriter) ID() backend.ID {
 	return bw.id
 }
 
-// SaveIndex saves all new indexes in the backend.
-func (r *Repository) SaveIndex() error {
-	for i, idx := range r.idx.NotFinalIndexes() {
+// saveIndex saves all indexes in the backend.
+func (r *Repository) saveIndex(indexes ...*Index) error {
+	for i, idx := range indexes {
 		debug.Log("Repo.SaveIndex", "Saving index %d", i)
 
 		blob, err := r.CreateEncryptedBlob(backend.Index)
@@ -541,6 +541,16 @@ func (r *Repository) SaveIndex() error {
 	return nil
 }
 
+// SaveIndex saves all new indexes in the backend.
+func (r *Repository) SaveIndex() error {
+	return r.saveIndex(r.idx.NotFinalIndexes()...)
+}
+
+// SaveFullIndex saves all full indexes in the backend.
+func (r *Repository) SaveFullIndex() error {
+	return r.saveIndex(r.idx.FullIndexes()...)
+}
+
 const loadIndexParallelism = 20
 
 // LoadIndex loads all index files from the backend in parallel and stores them