diff --git a/cmd/geth/main.go b/cmd/geth/main.go
index 9e5ae58570..e18b92a2ef 100644
--- a/cmd/geth/main.go
+++ b/cmd/geth/main.go
@@ -36,11 +36,13 @@ import (
 	"github.com/ethereum/go-ethereum/accounts"
 	"github.com/ethereum/go-ethereum/cmd/utils"
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/eth"
 	"github.com/ethereum/go-ethereum/logger"
 	"github.com/peterh/liner"
+	"path"
 )
 import _ "net/http/pprof"
 
@@ -208,12 +210,18 @@ JavaScript API. See https://github.com/ethereum/go-ethereum/wiki/Javascipt-Conso
 			Name:   "export",
 			Usage:  `export blockchain into file`,
 		},
+		{
+			Action: upgradeDb,
+			Name:   "upgradedb",
+			Usage:  "upgrade chainblock database",
+		},
 	}
 	app.Flags = []cli.Flag{
 		utils.UnlockedAccountFlag,
 		utils.PasswordFileFlag,
 		utils.BootnodesFlag,
 		utils.DataDirFlag,
+		utils.BlockchainVersionFlag,
 		utils.JSpathFlag,
 		utils.ListenPortFlag,
 		utils.MaxPeersFlag,
@@ -437,13 +445,29 @@ func importchain(ctx *cli.Context) {
 	if len(ctx.Args()) != 1 {
 		utils.Fatalf("This command requires an argument.")
 	}
-	chainmgr, _, _ := utils.GetChain(ctx)
+
+	cfg := utils.MakeEthConfig(ClientIdentifier, Version, ctx)
+	cfg.SkipBcVersionCheck = true
+
+	ethereum, err := eth.New(cfg)
+	if err != nil {
+		utils.Fatalf("%v\n", err)
+	}
+
+	chainmgr := ethereum.ChainManager()
 	start := time.Now()
-	err := utils.ImportChain(chainmgr, ctx.Args().First())
+	err = utils.ImportChain(chainmgr, ctx.Args().First())
 	if err != nil {
 		utils.Fatalf("Import error: %v\n", err)
 	}
+
+	// force database flush
+	ethereum.BlockDb().Close()
+	ethereum.StateDb().Close()
+	ethereum.ExtraDb().Close()
+
 	fmt.Printf("Import done in %v", time.Since(start))
+
 	return
 }
 
@@ -451,9 +475,18 @@ func exportchain(ctx *cli.Context) {
 	if len(ctx.Args()) != 1 {
 		utils.Fatalf("This command requires an argument.")
 	}
-	chainmgr, _, _ := utils.GetChain(ctx)
+
+	cfg := utils.MakeEthConfig(ClientIdentifier, Version, ctx)
+	cfg.SkipBcVersionCheck = true
+
+	ethereum, err := eth.New(cfg)
+	if err != nil {
+		utils.Fatalf("%v\n", err)
+	}
+
+	chainmgr := ethereum.ChainManager()
 	start := time.Now()
-	err := utils.ExportChain(chainmgr, ctx.Args().First())
+	err = utils.ExportChain(chainmgr, ctx.Args().First())
 	if err != nil {
 		utils.Fatalf("Export error: %v\n", err)
 	}
@@ -461,6 +494,60 @@ func exportchain(ctx *cli.Context) {
 	return
 }
 
+func upgradeDb(ctx *cli.Context) {
+	fmt.Println("Upgrade blockchain DB")
+
+	cfg := utils.MakeEthConfig(ClientIdentifier, Version, ctx)
+	cfg.SkipBcVersionCheck = true
+
+	ethereum, err := eth.New(cfg)
+	if err != nil {
+		utils.Fatalf("%v\n", err)
+	}
+
+	v, _ := ethereum.BlockDb().Get([]byte("BlockchainVersion"))
+	bcVersion := int(common.NewValue(v).Uint())
+
+	if bcVersion == 0 {
+		bcVersion = core.BlockChainVersion
+	}
+
+	filename := fmt.Sprintf("blockchain_%d_%s.chain", bcVersion, time.Now().Format("2006-01-02_15:04:05"))
+	exportFile := path.Join(ctx.GlobalString(utils.DataDirFlag.Name), filename)
+
+	err = utils.ExportChain(ethereum.ChainManager(), exportFile)
+	if err != nil {
+		utils.Fatalf("Unable to export chain for reimport %s\n", err)
+	}
+
+	ethereum.BlockDb().Close()
+	ethereum.StateDb().Close()
+	ethereum.ExtraDb().Close()
+
+	os.RemoveAll(path.Join(ctx.GlobalString(utils.DataDirFlag.Name), "blockchain"))
+
+	ethereum, err = eth.New(cfg)
+	if err != nil {
+		utils.Fatalf("%v\n", err)
+	}
+
+	ethereum.BlockDb().Put([]byte("BlockchainVersion"), common.NewValue(core.BlockChainVersion).Bytes())
+
+	err = utils.ImportChain(ethereum.ChainManager(), exportFile)
+	if err != nil {
+		utils.Fatalf("Import error %v (a backup is made in %s, use the import command to import it)\n", err, exportFile)
+	}
+
+	// force database flush
+	ethereum.BlockDb().Close()
+	ethereum.StateDb().Close()
+	ethereum.ExtraDb().Close()
+
+	os.Remove(exportFile)
+
+	fmt.Println("Import finished")
+}
+
 func dump(ctx *cli.Context) {
 	chainmgr, _, stateDb := utils.GetChain(ctx)
 	for _, arg := range ctx.Args() {
diff --git a/cmd/utils/cmd.go b/cmd/utils/cmd.go
index a6140d2331..7286f5c5e4 100644
--- a/cmd/utils/cmd.go
+++ b/cmd/utils/cmd.go
@@ -155,7 +155,11 @@ func ImportChain(chainmgr *core.ChainManager, fn string) error {
 
 	chainmgr.Reset()
 	stream := rlp.NewStream(fh)
-	var i int
+	var i, n int
+
+	batchSize := 2500
+	blocks := make(types.Blocks, batchSize)
+
 	for ; ; i++ {
 		var b types.Block
 		if err := stream.Decode(&b); err == io.EOF {
@@ -163,10 +167,25 @@ func ImportChain(chainmgr *core.ChainManager, fn string) error {
 		} else if err != nil {
 			return fmt.Errorf("at block %d: %v", i, err)
 		}
-		if err := chainmgr.InsertChain(types.Blocks{&b}); err != nil {
-			return fmt.Errorf("invalid block %d: %v", i, err)
+
+		blocks[n] = &b
+		n++
+
+		if n == batchSize {
+			if err := chainmgr.InsertChain(blocks); err != nil {
+				return fmt.Errorf("invalid block %v", err)
+			}
+			n = 0
+			blocks = make(types.Blocks, batchSize)
+		}
+	}
+
+	if n > 0 {
+		if err := chainmgr.InsertChain(blocks[:n]); err != nil {
+			return fmt.Errorf("invalid block %v", err)
 		}
 	}
+
 	fmt.Printf("imported %d blocks\n", i)
 	return nil
 }
diff --git a/cmd/utils/flags.go b/cmd/utils/flags.go
index 3ad06653e3..8141fae827 100644
--- a/cmd/utils/flags.go
+++ b/cmd/utils/flags.go
@@ -7,6 +7,7 @@ import (
 	"runtime"
 
 	"github.com/codegangsta/cli"
+	"github.com/ethereum/ethash"
 	"github.com/ethereum/go-ethereum/accounts"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core"
@@ -83,6 +84,11 @@ var (
 		Usage: "Network Id",
 		Value: eth.NetworkId,
 	}
+	BlockchainVersionFlag = cli.IntFlag{
+		Name:  "blockchainversion",
+		Usage: "Blockchain version",
+		Value: core.BlockChainVersion,
+	}
 
 	// miner settings
 	MinerThreadsFlag = cli.IntFlag{
@@ -237,29 +243,32 @@ func MakeEthConfig(clientID, version string, ctx *cli.Context) *eth.Config {
 	glog.SetLogDir(ctx.GlobalString(LogFileFlag.Name))
 
 	return &eth.Config{
-		Name:            common.MakeName(clientID, version),
-		DataDir:         ctx.GlobalString(DataDirFlag.Name),
-		ProtocolVersion: ctx.GlobalInt(ProtocolVersionFlag.Name),
-		NetworkId:       ctx.GlobalInt(NetworkIdFlag.Name),
-		LogFile:         ctx.GlobalString(LogFileFlag.Name),
-		LogLevel:        ctx.GlobalInt(LogLevelFlag.Name),
-		LogJSON:         ctx.GlobalString(LogJSONFlag.Name),
-		Etherbase:       ctx.GlobalString(EtherbaseFlag.Name),
-		MinerThreads:    ctx.GlobalInt(MinerThreadsFlag.Name),
-		AccountManager:  GetAccountManager(ctx),
-		VmDebug:         ctx.GlobalBool(VMDebugFlag.Name),
-		MaxPeers:        ctx.GlobalInt(MaxPeersFlag.Name),
-		Port:            ctx.GlobalString(ListenPortFlag.Name),
-		NAT:             GetNAT(ctx),
-		NodeKey:         GetNodeKey(ctx),
-		Shh:             true,
-		Dial:            true,
-		BootNodes:       ctx.GlobalString(BootnodesFlag.Name),
+		Name:               common.MakeName(clientID, version),
+		DataDir:            ctx.GlobalString(DataDirFlag.Name),
+		ProtocolVersion:    ctx.GlobalInt(ProtocolVersionFlag.Name),
+		BlockChainVersion:  ctx.GlobalInt(BlockchainVersionFlag.Name),
+		SkipBcVersionCheck: false,
+		NetworkId:          ctx.GlobalInt(NetworkIdFlag.Name),
+		LogFile:            ctx.GlobalString(LogFileFlag.Name),
+		LogLevel:           ctx.GlobalInt(LogLevelFlag.Name),
+		LogJSON:            ctx.GlobalString(LogJSONFlag.Name),
+		Etherbase:          ctx.GlobalString(EtherbaseFlag.Name),
+		MinerThreads:       ctx.GlobalInt(MinerThreadsFlag.Name),
+		AccountManager:     GetAccountManager(ctx),
+		VmDebug:            ctx.GlobalBool(VMDebugFlag.Name),
+		MaxPeers:           ctx.GlobalInt(MaxPeersFlag.Name),
+		Port:               ctx.GlobalString(ListenPortFlag.Name),
+		NAT:                GetNAT(ctx),
+		NodeKey:            GetNodeKey(ctx),
+		Shh:                true,
+		Dial:               true,
+		BootNodes:          ctx.GlobalString(BootnodesFlag.Name),
 	}
 }
 
 func GetChain(ctx *cli.Context) (*core.ChainManager, common.Database, common.Database) {
 	dataDir := ctx.GlobalString(DataDirFlag.Name)
+
 	blockDb, err := ethdb.NewLDBDatabase(path.Join(dataDir, "blockchain"))
 	if err != nil {
 		Fatalf("Could not open database: %v", err)
@@ -269,7 +278,20 @@ func GetChain(ctx *cli.Context) (*core.ChainManager, common.Database, common.Dat
 	if err != nil {
 		Fatalf("Could not open database: %v", err)
 	}
-	return core.NewChainManager(blockDb, stateDb, new(event.TypeMux)), blockDb, stateDb
+
+	extraDb, err := ethdb.NewLDBDatabase(path.Join(dataDir, "extra"))
+	if err != nil {
+		Fatalf("Could not open database: %v", err)
+	}
+
+	eventMux := new(event.TypeMux)
+	chainManager := core.NewChainManager(blockDb, stateDb, eventMux)
+	pow := ethash.New(chainManager)
+	txPool := core.NewTxPool(eventMux, chainManager.State)
+	blockProcessor := core.NewBlockProcessor(stateDb, extraDb, pow, txPool, chainManager, eventMux)
+	chainManager.SetProcessor(blockProcessor)
+
+	return chainManager, blockDb, stateDb
 }
 
 func GetAccountManager(ctx *cli.Context) *accounts.Manager {
diff --git a/core/block_processor.go b/core/block_processor.go
index 7aded346a7..d5a29b258c 100644
--- a/core/block_processor.go
+++ b/core/block_processor.go
@@ -18,6 +18,12 @@ import (
 	"gopkg.in/fatih/set.v0"
 )
 
+const (
+	// must be bumped when consensus algorithm is changed, this forces the upgradedb
+	// command to be run (forces the blocks to be imported again using the new algorithm)
+	BlockChainVersion = 1
+)
+
 var statelogger = logger.NewLogger("BLOCK")
 
 type BlockProcessor struct {
diff --git a/core/chain_manager.go b/core/chain_manager.go
index 5ad1dda832..25ee0eeeff 100644
--- a/core/chain_manager.go
+++ b/core/chain_manager.go
@@ -284,11 +284,14 @@ func (self *ChainManager) Export(w io.Writer) error {
 	defer self.mu.RUnlock()
 	glog.V(logger.Info).Infof("exporting %v blocks...\n", self.currentBlock.Header().Number)
 
-	for block := self.currentBlock; block != nil; block = self.GetBlock(block.Header().ParentHash) {
-		if err := block.EncodeRLP(w); err != nil {
+	last := self.currentBlock.NumberU64()
+
+	for nr := uint64(0); nr <= last; nr++ {
+		if err := self.GetBlockByNumber(nr).EncodeRLP(w); err != nil {
 			return err
 		}
 	}
+
 	return nil
 }
 
diff --git a/eth/backend.go b/eth/backend.go
index c7a5b233f0..f073ec6e62 100644
--- a/eth/backend.go
+++ b/eth/backend.go
@@ -42,6 +42,9 @@ type Config struct {
 	ProtocolVersion int
 	NetworkId       int
 
+	BlockChainVersion  int
+	SkipBcVersionCheck bool // e.g. blockchain export
+
 	DataDir  string
 	LogFile  string
 	LogLevel int
@@ -149,7 +152,7 @@ type Ethereum struct {
 }
 
 func New(config *Config) (*Ethereum, error) {
-	// Boostrap database
+	// Bootstrap database
 	logger.New(config.DataDir, config.LogFile, config.LogLevel)
 	if len(config.LogJSON) > 0 {
 		logger.NewJSONsystem(config.DataDir, config.LogJSON)
@@ -179,6 +182,16 @@ func New(config *Config) (*Ethereum, error) {
 	saveProtocolVersion(blockDb, config.ProtocolVersion)
 	glog.V(logger.Info).Infof("Protocol Version: %v, Network Id: %v", config.ProtocolVersion, config.NetworkId)
 
+	if !config.SkipBcVersionCheck {
+		b, _ := blockDb.Get([]byte("BlockchainVersion"))
+		bcVersion := int(common.NewValue(b).Uint())
+		if bcVersion != config.BlockChainVersion && bcVersion != 0 {
+			return nil, fmt.Errorf("Blockchain DB version mismatch (%d / %d). Run geth upgradedb.\n", bcVersion, config.BlockChainVersion)
+		}
+		saveBlockchainVersion(blockDb, config.BlockChainVersion)
+	}
+	glog.V(logger.Info).Infof("Blockchain DB Version: %d", config.BlockChainVersion)
+
 	eth := &Ethereum{
 		shutdownChan:   make(chan bool),
 		blockDb:        blockDb,
@@ -472,3 +485,12 @@ func saveProtocolVersion(db common.Database, protov int) {
 		db.Put([]byte("ProtocolVersion"), common.NewValue(protov).Bytes())
 	}
 }
+
+func saveBlockchainVersion(db common.Database, bcVersion int) {
+	d, _ := db.Get([]byte("BlockchainVersion"))
+	blockchainVersion := common.NewValue(d).Uint()
+
+	if blockchainVersion == 0 {
+		db.Put([]byte("BlockchainVersion"), common.NewValue(bcVersion).Bytes())
+	}
+}