diff --git a/pkg/api/types.go b/pkg/api/types.go
index 5cfd965..59576fb 100644
--- a/pkg/api/types.go
+++ b/pkg/api/types.go
@@ -351,7 +351,7 @@ type BackingStore interface {
 	Write([]byte, int64) error
 	DataSync() error
 	DataAdvise(int64, int64, uint32) error
-	Unmap() error
+	Unmap([]UnmapBlockDescriptor) error
 }
 
 type SCSIDeviceProtocol interface {
@@ -401,3 +401,8 @@ type SCSILu struct {
 }
 
 type LUNMap map[uint64]*SCSILu
+
+type UnmapBlockDescriptor struct {
+	Offset uint64
+	TL     uint32
+}
diff --git a/pkg/scsi/backingstore.go b/pkg/scsi/backingstore.go
index 6dcb541..f5d91b3 100644
--- a/pkg/scsi/backingstore.go
+++ b/pkg/scsi/backingstore.go
@@ -64,6 +64,7 @@ func bsPerformCommand(bs api.BackingStore, cmd *api.SCSICommand) (err error, key
 		rbuf, wbuf []byte
 		tl         int64 = int64(cmd.TL)
 	)
+
 	key = HARDWARE_ERROR
 	asc = ASC_INTERNAL_TGT_FAILURE
 	switch opcode {
@@ -134,12 +135,6 @@ func bsPerformCommand(bs api.BackingStore, cmd *api.SCSICommand) (err error, key
 		}
 		doVerify = true
 		goto verify
-	case api.UNMAP:
-		err = bs.Unmap()
-		if err != nil {
-			key = MEDIUM_ERROR
-			asc = NO_ADDITIONAL_SENSE
-		}
 	default:
 		break
 	}
diff --git a/pkg/scsi/backingstore/cephstore_linux.go b/pkg/scsi/backingstore/cephstore_linux.go
index c77820a..9e99f42 100644
--- a/pkg/scsi/backingstore/cephstore_linux.go
+++ b/pkg/scsi/backingstore/cephstore_linux.go
@@ -150,6 +150,6 @@ func (bs *CephBackingStore) DataAdvise(offset, length int64, advise uint32) erro
 	return nil
 }
 
-func (bs *CephBackingStore) Unmap() error {
+func (bs *CephBackingStore) Unmap([]api.UnmapBlockDescriptor) error {
 	return nil
 }
diff --git a/pkg/scsi/backingstore/common.go b/pkg/scsi/backingstore/common.go
index fc35bad..2a2d4b3 100644
--- a/pkg/scsi/backingstore/common.go
+++ b/pkg/scsi/backingstore/common.go
@@ -114,6 +114,6 @@ func (bs *FileBackingStore) DataAdvise(offset, length int64, advise uint32) erro
 	return util.Fadvise(bs.file, offset, length, advise)
 }
 
-func (bs *FileBackingStore) Unmap() error {
+func (bs *FileBackingStore) Unmap([]api.UnmapBlockDescriptor) error {
 	return nil
 }
diff --git a/pkg/scsi/backingstore/null.go b/pkg/scsi/backingstore/null.go
index f718d9a..8c74739 100644
--- a/pkg/scsi/backingstore/null.go
+++ b/pkg/scsi/backingstore/null.go
@@ -75,6 +75,6 @@ func (bs *NullBackingStore) DataAdvise(offset, length int64, advise uint32) erro
 	return nil
 }
 
-func (bs *NullBackingStore) Unmap() error {
+func (bs *NullBackingStore) Unmap([]api.UnmapBlockDescriptor) error {
 	return nil
 }
diff --git a/pkg/scsi/sbc.go b/pkg/scsi/sbc.go
index 36e668e..87ba500 100644
--- a/pkg/scsi/sbc.go
+++ b/pkg/scsi/sbc.go
@@ -18,6 +18,7 @@ limitations under the License.
 package scsi
 
 import (
+	"encoding/binary"
 	"fmt"
 	"unsafe"
 
@@ -295,13 +296,34 @@ sense:
 }
 
 func SBCUnmap(host int, cmd *api.SCSICommand) api.SAMStat {
-	err, key, asc := bsPerformCommand(cmd.Device.Storage, cmd)
-	if err == nil {
+	// check ANCHOR
+	if cmd.SCB[1]&0x01 != 0 {
+		BuildSenseData(cmd, ILLEGAL_REQUEST, ASC_INVALID_FIELD_IN_CDB)
+		return api.SAMStatCheckCondition
+	}
+
+	const blockDescLen = 16
+
+	var blockDescs []api.UnmapBlockDescriptor
+	for off := 8; uint32(off+blockDescLen) <= cmd.OutSDBBuffer.Length; off += blockDescLen {
+		lba := binary.BigEndian.Uint64(cmd.OutSDBBuffer.Buffer[off : off+8])
+		num := binary.BigEndian.Uint32(cmd.OutSDBBuffer.Buffer[off+8 : off+12])
+		blockDescs = append(blockDescs, api.UnmapBlockDescriptor{
+			Offset: lba << cmd.Device.BlockShift,
+			TL:     num << cmd.Device.BlockShift,
+		})
+	}
+
+	if len(blockDescs) == 0 {
 		return api.SAMStatGood
 	}
 
-	BuildSenseData(cmd, key, asc)
-	return api.SAMStatCheckCondition
+	if err := cmd.Device.Storage.Unmap(blockDescs); err != nil {
+		BuildSenseData(cmd, MEDIUM_ERROR, NO_ADDITIONAL_SENSE)
+		return api.SAMStatCheckCondition
+	}
+
+	return api.SAMStatGood
 }
 
 /*