Index: sys/dev/md/md.c
===================================================================
--- sys/dev/md/md.c
+++ sys/dev/md/md.c
@@ -207,6 +207,7 @@
 	unsigned opencount;
 	unsigned fwheads;
 	unsigned fwsectors;
+	char ident[32];
 	unsigned flags;
 	char name[20];
 	struct proc *procp;
@@ -1178,6 +1179,8 @@
 			    sc->fwheads))) ||
 			    g_handleattr_int(bp, "GEOM::candelete", 1))
 				error = -1;
+			else if (g_handleattr_str(bp, "GEOM::ident", sc->ident))
+				error = -1;
 			else if (g_handleattr_int(bp, "MNT::verified", isv))
 				error = -1;
 			else
@@ -1294,6 +1297,7 @@
 		sc->fwsectors = mdio->md_fwsectors;
 	if (mdio->md_fwheads != 0)
 		sc->fwheads = mdio->md_fwheads;
+	snprintf(sc->ident, sizeof(sc->ident), "MD-%u", arc4random());
 	sc->flags = mdio->md_options & (MD_COMPRESS | MD_FORCE);
 	sc->indir = dimension(sc->mediasize / sc->sectorsize);
 	sc->uma = uma_zcreate(sc->name, sc->sectorsize, NULL, NULL, NULL, NULL,
@@ -1411,6 +1415,8 @@
 		sc->fwsectors = mdio->md_fwsectors;
 	if (mdio->md_fwheads != 0)
 		sc->fwheads = mdio->md_fwheads;
+	snprintf(sc->ident, sizeof(sc->ident), "MD-DEV%lu-INO%lu",
+	    vattr.va_fsid, vattr.va_fileid);
 	sc->flags = mdio->md_options & (MD_FORCE | MD_ASYNC | MD_VERIFY);
 	if (!(flags & FWRITE))
 		sc->flags |= MD_READONLY;
@@ -1561,6 +1567,7 @@
 		sc->fwsectors = mdio->md_fwsectors;
 	if (mdio->md_fwheads != 0)
 		sc->fwheads = mdio->md_fwheads;
+	snprintf(sc->ident, sizeof(sc->ident), "MD-%u", arc4random());
 	sc->object = vm_pager_allocate(OBJT_SWAP, NULL, PAGE_SIZE * npage,
 	    VM_PROT_DEFAULT, 0, td->td_ucred);
 	if (sc->object == NULL)
@@ -1592,6 +1599,8 @@
 	if (sc->mediasize <= 0 || (sc->mediasize % PAGE_SIZE) != 0)
 		return (EDOM);
 
+	snprintf(sc->ident, sizeof(sc->ident), "MD-NULL");
+
 	return (0);
 }
 
@@ -1895,6 +1904,9 @@
 			    indent, (uintmax_t) mp->fwheads);
 			sbuf_printf(sb, "%s<fwsectors>%ju</fwsectors>\n",
 			    indent, (uintmax_t) mp->fwsectors);
+                        sbuf_printf(sb, "%s<ident>", indent);
+                        g_conf_printf_escaped(sb, "%s", mp->ident);
+                        sbuf_printf(sb, "</ident>\n");
 			sbuf_printf(sb, "%s<length>%ju</length>\n",
 			    indent, (uintmax_t) mp->mediasize);
 			sbuf_printf(sb, "%s<compression>%s</compression>\n", indent,