diff --git a/sys/boot/zfs/zfsimpl.c b/sys/boot/zfs/zfsimpl.c
index ff567a4..6a18b44 100644
--- a/sys/boot/zfs/zfsimpl.c
+++ b/sys/boot/zfs/zfsimpl.c
@@ -53,6 +53,8 @@ static char *zfs_temp_buf, *zfs_temp_end, *zfs_temp_ptr;
 
 #define TEMP_SIZE	(1*SPA_MAXBLOCKSIZE)
 
+static int zio_read(spa_t *spa, const blkptr_t *bp, void *buf);
+
 static void
 zfs_init(void)
 {
@@ -897,6 +899,33 @@ ilog2(int n)
 }
 
 static int
+zio_read_gang(spa_t *spa, const blkptr_t *bp, const dva_t *dva, void *buf)
+{
+	zio_gbh_phys_t zio_gb;
+	vdev_t *vdev;
+	int vdevid;
+	off_t offset;
+	int i;
+
+	vdevid = DVA_GET_VDEV(dva);
+	offset = DVA_GET_OFFSET(dva);
+	STAILQ_FOREACH(vdev, &spa->spa_vdevs, v_childlink)
+		if (vdev->v_id == vdevid)
+			break;
+	if (!vdev || !vdev->v_read)
+		return (EIO);
+	if (vdev->v_read(vdev, bp, &zio_gb, offset, SPA_GANGBLOCKSIZE))
+		return (EIO);
+
+	for (i = 0; i < SPA_GBH_NBLKPTRS; i++) {
+		if (zio_read(spa, &zio_gb.zg_blkptr[i], buf))
+			return (EIO);
+	}
+ 
+	return (0);
+}
+
+static int
 zio_read(spa_t *spa, const blkptr_t *bp, void *buf)
 {
 	int cpfunc = BP_GET_COMPRESS(bp);
@@ -920,20 +949,26 @@ zio_read(spa_t *spa, const blkptr_t *bp, void *buf)
 		if (!dva->dva_word[0] && !dva->dva_word[1])
 			continue;
 
-		vdevid = DVA_GET_VDEV(dva);
-		offset = DVA_GET_OFFSET(dva);
-		STAILQ_FOREACH(vdev, &spa->spa_vdevs, v_childlink)
-			if (vdev->v_id == vdevid)
-				break;
-		if (!vdev || !vdev->v_read)
-			continue;
-		if (vdev->v_read(vdev, bp, pbuf, offset, psize))
-			continue;
+		if (DVA_GET_GANG(dva)) {
+			printf("ZFS: gang block detected!\n");
+			if (zio_read_gang(spa, bp, dva, buf))
+				return (EIO); 
+		} else {
+			vdevid = DVA_GET_VDEV(dva);
+			offset = DVA_GET_OFFSET(dva);
+			STAILQ_FOREACH(vdev, &spa->spa_vdevs, v_childlink)
+				if (vdev->v_id == vdevid)
+					break;
+			if (!vdev || !vdev->v_read)
+				continue;
+			if (vdev->v_read(vdev, bp, pbuf, offset, psize))
+				continue;
 
-		if (cpfunc != ZIO_COMPRESS_OFF) {
-			if (zio_decompress_data(cpfunc, pbuf, psize,
-				buf, lsize))
-				return (EIO);
+			if (cpfunc != ZIO_COMPRESS_OFF) {
+				if (zio_decompress_data(cpfunc, pbuf, psize,
+				    buf, lsize))
+					return (EIO);
+			}
 		}
 
 		return (0);
diff --git a/sys/cddl/boot/zfs/zfsimpl.h b/sys/cddl/boot/zfs/zfsimpl.h
index a0b7b72..688bb5c 100644
--- a/sys/cddl/boot/zfs/zfsimpl.h
+++ b/sys/cddl/boot/zfs/zfsimpl.h
@@ -374,6 +374,24 @@ typedef struct vdev_label {
 #define	VDEV_LABEL_END_SIZE	(2 * sizeof (vdev_label_t))
 #define	VDEV_LABELS		4
 
+/*
+ * Gang block headers are self-checksumming and contain an array
+ * of block pointers.
+ */
+#define SPA_GANGBLOCKSIZE	SPA_MINBLOCKSIZE
+#define SPA_GBH_NBLKPTRS	((SPA_GANGBLOCKSIZE - \
+	sizeof (zio_block_tail_t)) / sizeof (blkptr_t))
+#define SPA_GBH_FILLER		((SPA_GANGBLOCKSIZE - \
+	sizeof (zio_block_tail_t) - \
+	(SPA_GBH_NBLKPTRS * sizeof (blkptr_t))) /\
+	sizeof (uint64_t))
+
+typedef struct zio_gbh {
+	blkptr_t		zg_blkptr[SPA_GBH_NBLKPTRS];
+	uint64_t		zg_filler[SPA_GBH_FILLER];
+	zio_block_tail_t	zg_tail;
+} zio_gbh_phys_t;
+
 enum zio_checksum {
 	ZIO_CHECKSUM_INHERIT = 0,
 	ZIO_CHECKSUM_ON,