diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index d64084a900..5394875252 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -975,9 +975,7 @@ void virDomainDiskDefFree(virDomainDiskDefPtr def)
     VIR_FREE(def->src);
     VIR_FREE(def->dst);
     VIR_FREE(def->driverName);
-    VIR_FREE(def->driverType);
     VIR_FREE(def->mirror);
-    VIR_FREE(def->mirrorFormat);
     VIR_FREE(def->auth.username);
     VIR_FREE(def->wwn);
     if (def->auth.secretType == VIR_DOMAIN_DISK_SECRET_TYPE_USAGE)
@@ -4176,12 +4174,8 @@ virDomainDiskDefParseXML(virCapsPtr caps,
     authUsername = NULL;
     def->driverName = driverName;
     driverName = NULL;
-    def->driverType = driverType;
-    driverType = NULL;
     def->mirror = mirror;
     mirror = NULL;
-    def->mirrorFormat = mirrorFormat;
-    mirrorFormat = NULL;
     def->mirroring = mirroring;
     def->encryption = encryption;
     encryption = NULL;
@@ -4190,23 +4184,35 @@ virDomainDiskDefParseXML(virCapsPtr caps,
     def->wwn = wwn;
     wwn = NULL;
 
-    if (!def->driverType &&
-        caps->defaultDiskDriverType &&
-        !(def->driverType = strdup(virStorageFileFormatTypeToString(
-                                       caps->defaultDiskDriverType))))
-        goto no_memory;
+    if (driverType) {
+        def->format = virStorageFileFormatTypeFromString(driverType);
+        if (def->format <= 0) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                           _("unknown driver format value '%s'"),
+                           driverType);
+            goto error;
+        }
+    } else if (def->type == VIR_DOMAIN_DISK_TYPE_FILE ||
+               def->type == VIR_DOMAIN_DISK_TYPE_BLOCK) {
+        def->format = caps->defaultDiskDriverType;
+    }
 
     if (!def->driverName &&
         caps->defaultDiskDriverName &&
         !(def->driverName = strdup(caps->defaultDiskDriverName)))
         goto no_memory;
 
-
-    if (def->mirror && !def->mirrorFormat &&
-        caps->defaultDiskDriverType &&
-        !(def->mirrorFormat = strdup(virStorageFileFormatTypeToString(
-                                         caps->defaultDiskDriverType))))
-        goto no_memory;
+    if (mirrorFormat) {
+        def->mirrorFormat = virStorageFileFormatTypeFromString(mirrorFormat);
+        if (def->mirrorFormat <= 0) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                           _("unknown mirror format value '%s'"),
+                           driverType);
+            goto error;
+        }
+    } else if (def->mirror) {
+        def->mirrorFormat = caps->defaultDiskDriverType;
+    }
 
     if (def->info.type == VIR_DOMAIN_DEVICE_ADDRESS_TYPE_NONE
         && virDomainDiskDefAssignAddress(caps, def) < 0)
@@ -11865,13 +11871,14 @@ virDomainDiskDefFormat(virBufferPtr buf,
                           virDomainSnapshotLocationTypeToString(def->snapshot));
     virBufferAddLit(buf, ">\n");
 
-    if (def->driverName || def->driverType || def->cachemode ||
+    if (def->driverName || def->format > 0 || def->cachemode ||
         def->ioeventfd || def->event_idx || def->copy_on_read) {
         virBufferAddLit(buf, "      <driver");
         if (def->driverName)
             virBufferAsprintf(buf, " name='%s'", def->driverName);
-        if (def->driverType)
-            virBufferAsprintf(buf, " type='%s'", def->driverType);
+        if (def->format > 0)
+            virBufferAsprintf(buf, " type='%s'",
+                              virStorageFileFormatTypeToString(def->format));
         if (def->cachemode)
             virBufferAsprintf(buf, " cache='%s'", cachemode);
         if (def->error_policy)
@@ -11983,7 +11990,8 @@ virDomainDiskDefFormat(virBufferPtr buf,
     if (def->mirror && !(flags & VIR_DOMAIN_XML_INACTIVE)) {
         virBufferEscapeString(buf, "      <mirror file='%s'", def->mirror);
         if (def->mirrorFormat)
-            virBufferAsprintf(buf, " format='%s'", def->mirrorFormat);
+            virBufferAsprintf(buf, " format='%s'",
+                              virStorageFileFormatTypeToString(def->mirrorFormat));
         if (def->mirroring)
             virBufferAddLit(buf, " ready='yes'");
         virBufferAddLit(buf, "/>\n");
@@ -14850,15 +14858,8 @@ int virDomainDiskDefForeachPath(virDomainDiskDefPtr disk,
         return ret;
     }
 
-    if (disk->driverType) {
-        const char *formatStr = disk->driverType;
-
-        if ((format = virStorageFileFormatTypeFromString(formatStr)) <= 0) {
-            virReportError(VIR_ERR_INTERNAL_ERROR,
-                           _("unknown disk format '%s' for %s"),
-                           disk->driverType, disk->src);
-            goto cleanup;
-        }
+    if (disk->format > 0) {
+        format = disk->format;
     } else {
         if (allowProbing) {
             format = VIR_STORAGE_FILE_AUTO;
diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
index ac6311fc6a..039e34ddc1 100644
--- a/src/conf/domain_conf.h
+++ b/src/conf/domain_conf.h
@@ -567,10 +567,10 @@ struct _virDomainDiskDef {
         } secret;
     } auth;
     char *driverName;
-    char *driverType;
+    int format; /* enum virStorageFileFormat */
 
     char *mirror;
-    char *mirrorFormat;
+    int mirrorFormat; /* enum virStorageFileFormat */
     bool mirroring;
 
     struct {
diff --git a/src/libxl/libxl_conf.c b/src/libxl/libxl_conf.c
index b988fa7aef..fa931c38b8 100644
--- a/src/libxl/libxl_conf.c
+++ b/src/libxl/libxl_conf.c
@@ -41,6 +41,7 @@
 #include "capabilities.h"
 #include "libxl_driver.h"
 #include "libxl_conf.h"
+#include "storage_file.h"
 
 
 #define VIR_FROM_THIS VIR_FROM_LIBXL
@@ -505,25 +506,30 @@ libxlMakeDisk(virDomainDefPtr def, virDomainDiskDefPtr l_disk,
     if (l_disk->driverName) {
         if (STREQ(l_disk->driverName, "tap") ||
             STREQ(l_disk->driverName, "tap2")) {
-            if (l_disk->driverType) {
-                if (STREQ(l_disk->driverType, "qcow")) {
-                    x_disk->format = DISK_FORMAT_QCOW;
-                    x_disk->backend = DISK_BACKEND_QDISK;
-                } else if (STREQ(l_disk->driverType, "qcow2")) {
-                    x_disk->format = DISK_FORMAT_QCOW2;
-                    x_disk->backend = DISK_BACKEND_QDISK;
-                } else if (STREQ(l_disk->driverType, "vhd")) {
-                    x_disk->format = DISK_FORMAT_VHD;
-                    x_disk->backend = DISK_BACKEND_TAP;
-                } else if (STREQ(l_disk->driverType, "aio") ||
-                            STREQ(l_disk->driverType, "raw")) {
-                    x_disk->format = DISK_FORMAT_RAW;
-                    x_disk->backend = DISK_BACKEND_TAP;
-                }
-            } else {
+            switch (l_disk->format) {
+            case VIR_STORAGE_FILE_QCOW:
+                x_disk->format = DISK_FORMAT_QCOW;
+                x_disk->backend = DISK_BACKEND_QDISK;
+                break;
+            case VIR_STORAGE_FILE_QCOW2:
+                x_disk->format = DISK_FORMAT_QCOW2;
+                x_disk->backend = DISK_BACKEND_QDISK;
+                break;
+            case VIR_STORAGE_FILE_VHD:
+                x_disk->format = DISK_FORMAT_VHD;
+                x_disk->backend = DISK_BACKEND_TAP;
+                break;
+            case VIR_STORAGE_FILE_NONE:
                 /* No subtype specified, default to raw/tap */
-                    x_disk->format = DISK_FORMAT_RAW;
-                    x_disk->backend = DISK_BACKEND_TAP;
+            case VIR_STORAGE_FILE_RAW:
+                x_disk->format = DISK_FORMAT_RAW;
+                x_disk->backend = DISK_BACKEND_TAP;
+                break;
+            default:
+                virReportError(VIR_ERR_INTERNAL_ERROR,
+                               _("libxenlight does not support disk driver %s"),
+                               virStorageFileFormatTypeToString(l_disk->format));
+                return -1;
             }
         } else if (STREQ(l_disk->driverName, "file")) {
             x_disk->format = DISK_FORMAT_RAW;
diff --git a/src/libxl/libxl_driver.c b/src/libxl/libxl_driver.c
index 6fe284f8a9..f4e9aa669b 100644
--- a/src/libxl/libxl_driver.c
+++ b/src/libxl/libxl_driver.c
@@ -3202,11 +3202,7 @@ libxlDomainUpdateDeviceConfig(virDomainDefPtr vmdef, virDomainDeviceDefPtr dev)
                 orig->driverName = disk->driverName;
                 disk->driverName = NULL;
             }
-            if (disk->driverType) {
-                VIR_FREE(orig->driverType);
-                orig->driverType = disk->driverType;
-                disk->driverType = NULL;
-            }
+            orig->format = disk->format;
             disk->src = NULL;
             break;
         default:
diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index 0623c58a4c..5a5a2fabba 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -43,6 +43,7 @@
 #include "virnetdevtap.h"
 #include "base64.h"
 #include "device_conf.h"
+#include "storage_file.h"
 
 #include <sys/utsname.h>
 #include <sys/stat.h>
@@ -2142,11 +2143,10 @@ qemuBuildDriveStr(virConnectPtr conn ATTRIBUTE_UNUSED,
           disk->tray_status == VIR_DOMAIN_DISK_TRAY_OPEN)) {
         if (disk->type == VIR_DOMAIN_DISK_TYPE_DIR) {
             /* QEMU only supports magic FAT format for now */
-            if (disk->driverType &&
-                STRNEQ(disk->driverType, "fat")) {
+            if (disk->format > 0 && disk->format != VIR_STORAGE_FILE_FAT) {
                 virReportError(VIR_ERR_INTERNAL_ERROR,
                                _("unsupported disk driver type for '%s'"),
-                               disk->driverType);
+                               virStorageFileFormatTypeToString(disk->format));
                 goto error;
             }
             if (!disk->readonly) {
@@ -2243,10 +2243,11 @@ qemuBuildDriveStr(virConnectPtr conn ATTRIBUTE_UNUSED,
                        _("transient disks not supported yet"));
         goto error;
     }
-    if (disk->driverType && *disk->driverType != '\0' &&
+    if (disk->format > 0 &&
         disk->type != VIR_DOMAIN_DISK_TYPE_DIR &&
         qemuCapsGet(caps, QEMU_CAPS_DRIVE_FORMAT))
-        virBufferAsprintf(&opt, ",format=%s", disk->driverType);
+        virBufferAsprintf(&opt, ",format=%s",
+                          virStorageFileFormatTypeToString(disk->format));
 
     /* generate geometry command string */
     if (disk->geometry.cylinders > 0 &&
@@ -5244,11 +5245,10 @@ qemuBuildCommandLine(virConnectPtr conn,
 
             if (disk->type == VIR_DOMAIN_DISK_TYPE_DIR) {
                 /* QEMU only supports magic FAT format for now */
-                if (disk->driverType &&
-                    STRNEQ(disk->driverType, "fat")) {
+                if (disk->format > 0 && disk->format != VIR_STORAGE_FILE_FAT) {
                     virReportError(VIR_ERR_INTERNAL_ERROR,
                                    _("unsupported disk driver type for '%s'"),
-                                   disk->driverType);
+                                   virStorageFileFormatTypeToString(disk->format));
                     goto error;
                 }
                 if (!disk->readonly) {
@@ -7055,7 +7055,7 @@ qemuParseCommandLineDisk(virCapsPtr caps,
                 virReportOOMError();
                 goto cleanup;
             }
-            def->driverType = values[i];
+            def->format = virStorageFileFormatTypeFromString(values[i]);
             values[i] = NULL;
         } else if (STREQ(keywords[i], "cache")) {
             if (STREQ(values[i], "off") ||
diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index cbc621f1a0..fb775c13c7 100644
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -36,6 +36,7 @@
 #include "virfile.h"
 #include "domain_event.h"
 #include "virtime.h"
+#include "storage_file.h"
 
 #include <sys/time.h>
 #include <fcntl.h>
@@ -1410,7 +1411,7 @@ void qemuDomainObjCheckDiskTaint(struct qemud_driver *driver,
                                  virDomainDiskDefPtr disk,
                                  int logFD)
 {
-    if (!disk->driverType &&
+    if ((!disk->format || disk->format == VIR_STORAGE_FILE_AUTO) &&
         driver->allowDiskFormatProbing)
         qemuDomainObjTaint(driver, obj, VIR_DOMAIN_TAINT_DISK_PROBING, logFD);
 
@@ -1662,8 +1663,8 @@ qemuDomainSnapshotForEachQcow2Raw(struct qemud_driver *driver,
     for (i = 0; i < ndisks; i++) {
         /* FIXME: we also need to handle LVM here */
         if (def->disks[i]->device == VIR_DOMAIN_DISK_DEVICE_DISK) {
-            if (!def->disks[i]->driverType ||
-                STRNEQ(def->disks[i]->driverType, "qcow2")) {
+            if (def->disks[i]->format > 0 &&
+                def->disks[i]->format != VIR_STORAGE_FILE_QCOW2) {
                 if (try_all) {
                     /* Continue on even in the face of error, since other
                      * disks in this VM may have the same snapshot name.
diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 78e939e6ec..40b908a7f0 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -6335,11 +6335,8 @@ qemuDomainUpdateDeviceConfig(qemuCapsPtr caps,
             orig->driverName = disk->driverName;
             disk->driverName = NULL;
         }
-        if (disk->driverType) {
-            VIR_FREE(orig->driverType);
-            orig->driverType = disk->driverType;
-            disk->driverType = NULL;
-        }
+        if (disk->format)
+            orig->format = disk->format;
         disk->src = NULL;
         break;
 
@@ -9302,13 +9299,8 @@ static int qemuDomainGetBlockInfo(virDomainPtr dom,
     }
 
     /* Probe for magic formats */
-    if (disk->driverType) {
-        if ((format = virStorageFileFormatTypeFromString(disk->driverType)) <= 0) {
-            virReportError(VIR_ERR_INTERNAL_ERROR,
-                           _("unknown disk format %s for %s"),
-                           disk->driverType, disk->src);
-            goto cleanup;
-        }
+    if (disk->format) {
+        format = disk->format;
     } else {
         if (driver->allowDiskFormatProbing) {
             if ((format = virStorageFileProbeFormat(disk->src)) < 0)
@@ -10481,7 +10473,7 @@ qemuDomainSnapshotIsAllowed(virDomainObjPtr vm)
 
         if ((disk->device == VIR_DOMAIN_DISK_DEVICE_LUN) ||
             (disk->device == VIR_DOMAIN_DISK_DEVICE_DISK &&
-             STRNEQ_NULLABLE(disk->driverType, "qcow2"))) {
+             disk->format > 0 && disk->format != VIR_STORAGE_FILE_QCOW2)) {
             virReportError(VIR_ERR_OPERATION_INVALID,
                            _("Disk '%s' does not support snapshotting"),
                            disk->src);
@@ -10675,13 +10667,14 @@ qemuDomainSnapshotDiskPrepare(virDomainObjPtr vm, virDomainSnapshotDefPtr def,
                                disk->name);
                 goto cleanup;
             }
-            if (!vm->def->disks[i]->driverType ||
-                STRNEQ(vm->def->disks[i]->driverType, "qcow2")) {
+            if (vm->def->disks[i]->format > 0 &&
+                vm->def->disks[i]->format != VIR_STORAGE_FILE_QCOW2) {
                 virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
                                _("internal snapshot for disk %s unsupported "
                                  "for storage type %s"),
                                disk->name,
-                               NULLSTR(vm->def->disks[i]->driverType));
+                               virStorageFileFormatTypeToString(
+                                   vm->def->disks[i]->format));
                 goto cleanup;
             }
             found = true;
@@ -10768,13 +10761,12 @@ qemuDomainSnapshotCreateSingleDiskActive(struct qemud_driver *driver,
     qemuDomainObjPrivatePtr priv = vm->privateData;
     char *device = NULL;
     char *source = NULL;
-    char *driverType = NULL;
+    int format = VIR_STORAGE_FILE_NONE;
     char *persistSource = NULL;
-    char *persistDriverType = NULL;
     int ret = -1;
     int fd = -1;
     char *origsrc = NULL;
-    char *origdriver = NULL;
+    int origdriver;
     bool need_unlink = false;
 
     if (snap->snapshot != VIR_DOMAIN_SNAPSHOT_LOCATION_EXTERNAL) {
@@ -10783,14 +10775,19 @@ qemuDomainSnapshotCreateSingleDiskActive(struct qemud_driver *driver,
         return -1;
     }
 
+    if (snap->driverType) {
+        format = virStorageFileFormatTypeFromString(snap->driverType);
+        if (format <= 0) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                           _("unknown driver type %s"), snap->driverType);
+            goto cleanup;
+        }
+    }
+
     if (virAsprintf(&device, "drive-%s", disk->info.alias) < 0 ||
         !(source = strdup(snap->file)) ||
-        (STRNEQ_NULLABLE(disk->driverType, snap->driverType) &&
-         !(driverType = strdup(snap->driverType))) ||
         (persistDisk &&
-         (!(persistSource = strdup(source)) ||
-          (STRNEQ_NULLABLE(persistDisk->driverType, snap->driverType) &&
-           !(persistDriverType = strdup(snap->driverType)))))) {
+         !(persistSource = strdup(source)))) {
         virReportOOMError();
         goto cleanup;
     }
@@ -10807,8 +10804,8 @@ qemuDomainSnapshotCreateSingleDiskActive(struct qemud_driver *driver,
 
     origsrc = disk->src;
     disk->src = source;
-    origdriver = disk->driverType;
-    disk->driverType = (char *) "raw"; /* Don't want to probe backing files */
+    origdriver = disk->format;
+    disk->format = VIR_STORAGE_FILE_RAW; /* Don't want to probe backing files */
 
     if (virDomainLockDiskAttach(driver->lockManager, driver->uri,
                                 vm, disk) < 0)
@@ -10829,8 +10826,7 @@ qemuDomainSnapshotCreateSingleDiskActive(struct qemud_driver *driver,
 
     disk->src = origsrc;
     origsrc = NULL;
-    disk->driverType = origdriver;
-    origdriver = NULL;
+    disk->format = origdriver;
 
     /* create the actual snapshot */
     ret = qemuMonitorDiskSnapshot(priv->mon, actions, device, source,
@@ -10844,34 +10840,24 @@ qemuDomainSnapshotCreateSingleDiskActive(struct qemud_driver *driver,
     VIR_FREE(disk->src);
     disk->src = source;
     source = NULL;
-    if (driverType) {
-        VIR_FREE(disk->driverType);
-        disk->driverType = driverType;
-        driverType = NULL;
-    }
+    disk->format = format;
     if (persistDisk) {
         VIR_FREE(persistDisk->src);
         persistDisk->src = persistSource;
         persistSource = NULL;
-        if (persistDriverType) {
-            VIR_FREE(persistDisk->driverType);
-            persistDisk->driverType = persistDriverType;
-            persistDriverType = NULL;
-        }
+        persistDisk->format = format;
     }
 
 cleanup:
     if (origsrc) {
         disk->src = origsrc;
-        disk->driverType = origdriver;
+        disk->format = origdriver;
     }
     if (need_unlink && unlink(source))
         VIR_WARN("unable to unlink just-created %s", source);
     VIR_FREE(device);
     VIR_FREE(source);
-    VIR_FREE(driverType);
     VIR_FREE(persistSource);
-    VIR_FREE(persistDriverType);
     return ret;
 }
 
@@ -10888,17 +10874,12 @@ qemuDomainSnapshotUndoSingleDiskActive(struct qemud_driver *driver,
                                        bool need_unlink)
 {
     char *source = NULL;
-    char *driverType = NULL;
     char *persistSource = NULL;
-    char *persistDriverType = NULL;
     struct stat st;
 
     if (!(source = strdup(origdisk->src)) ||
-        (origdisk->driverType &&
-         !(driverType = strdup(origdisk->driverType))) ||
         (persistDisk &&
-         (!(persistSource = strdup(source)) ||
-          (driverType && !(persistDriverType = strdup(driverType)))))) {
+         !(persistSource = strdup(source)))) {
         virReportOOMError();
         goto cleanup;
     }
@@ -10918,27 +10899,17 @@ qemuDomainSnapshotUndoSingleDiskActive(struct qemud_driver *driver,
     VIR_FREE(disk->src);
     disk->src = source;
     source = NULL;
-    VIR_FREE(disk->driverType);
-    if (driverType) {
-        disk->driverType = driverType;
-        driverType = NULL;
-    }
+    disk->format = origdisk->format;
     if (persistDisk) {
         VIR_FREE(persistDisk->src);
         persistDisk->src = persistSource;
         persistSource = NULL;
-        VIR_FREE(persistDisk->driverType);
-        if (persistDriverType) {
-            persistDisk->driverType = persistDriverType;
-            persistDriverType = NULL;
-        }
+        persistDisk->format = origdisk->format;
     }
 
 cleanup:
     VIR_FREE(source);
-    VIR_FREE(driverType);
     VIR_FREE(persistSource);
-    VIR_FREE(persistDriverType);
 }
 
 /* The domain is expected to be locked and active. */
diff --git a/src/qemu/qemu_hotplug.c b/src/qemu/qemu_hotplug.c
index 25540bd599..ca441f23b6 100644
--- a/src/qemu/qemu_hotplug.c
+++ b/src/qemu/qemu_hotplug.c
@@ -45,6 +45,7 @@
 #include "virnetdevbridge.h"
 #include "virnetdevtap.h"
 #include "device_conf.h"
+#include "storage_file.h"
 
 #define VIR_FROM_THIS VIR_FROM_QEMU
 
@@ -107,10 +108,10 @@ int qemuDomainChangeEjectableMedia(struct qemud_driver *driver,
     if (disk->src) {
         const char *format = NULL;
         if (disk->type != VIR_DOMAIN_DISK_TYPE_DIR) {
-            if (disk->driverType)
-                format = disk->driverType;
-            else if (origdisk->driverType)
-                format = origdisk->driverType;
+            if (disk->format > 0)
+                format = virStorageFileFormatTypeToString(disk->format);
+            else if (origdisk->format > 0)
+                format = virStorageFileFormatTypeToString(origdisk->format);
         }
         ret = qemuMonitorChangeMedia(priv->mon,
                                      driveAlias,
diff --git a/src/vbox/vbox_tmpl.c b/src/vbox/vbox_tmpl.c
index 0eeac85c9c..32a903e8fe 100644
--- a/src/vbox/vbox_tmpl.c
+++ b/src/vbox/vbox_tmpl.c
@@ -3846,7 +3846,8 @@ vboxAttachDrives(virDomainDefPtr def, vboxGlobalData *data, IMachine *machine)
         VIR_DEBUG("disk(%d) src:        %s", i, def->disks[i]->src);
         VIR_DEBUG("disk(%d) dst:        %s", i, def->disks[i]->dst);
         VIR_DEBUG("disk(%d) driverName: %s", i, def->disks[i]->driverName);
-        VIR_DEBUG("disk(%d) driverType: %s", i, def->disks[i]->driverType);
+        VIR_DEBUG("disk(%d) driverType: %s", i,
+                  virStorageFileFormatTypeToString(def->disks[i]->format));
         VIR_DEBUG("disk(%d) cachemode:  %d", i, def->disks[i]->cachemode);
         VIR_DEBUG("disk(%d) readonly:   %s", i, (def->disks[i]->readonly
                                              ? "True" : "False"));
@@ -4125,7 +4126,8 @@ vboxAttachDrives(virDomainDefPtr def, vboxGlobalData *data, IMachine *machine)
         VIR_DEBUG("disk(%d) src:        %s", i, def->disks[i]->src);
         VIR_DEBUG("disk(%d) dst:        %s", i, def->disks[i]->dst);
         VIR_DEBUG("disk(%d) driverName: %s", i, def->disks[i]->driverName);
-        VIR_DEBUG("disk(%d) driverType: %s", i, def->disks[i]->driverType);
+        VIR_DEBUG("disk(%d) driverType: %s", i,
+                  virStorageFileFormatTypeToString(def->disks[i]->format));
         VIR_DEBUG("disk(%d) cachemode:  %d", i, def->disks[i]->cachemode);
         VIR_DEBUG("disk(%d) readonly:   %s", i, (def->disks[i]->readonly
                                              ? "True" : "False"));
diff --git a/src/xenxs/xen_sxpr.c b/src/xenxs/xen_sxpr.c
index 38a7e137d7..35ad496c75 100644
--- a/src/xenxs/xen_sxpr.c
+++ b/src/xenxs/xen_sxpr.c
@@ -36,6 +36,7 @@
 #include "count-one-bits.h"
 #include "xenxs_private.h"
 #include "xen_sxpr.h"
+#include "storage_file.h"
 
 /* Get a domain id from a S-expression string */
 int xenGetDomIdFromSxprString(const char *sexpr, int xendConfigVersion)
@@ -427,6 +428,8 @@ xenParseSxprDisks(virDomainDefPtr def,
 
                 if (STREQ (disk->driverName, "tap") ||
                     STREQ (disk->driverName, "tap2")) {
+                    char *driverType = NULL;
+
                     offset = strchr(src, ':');
                     if (!offset) {
                         virReportError(VIR_ERR_INTERNAL_ERROR,
@@ -434,21 +437,19 @@ xenParseSxprDisks(virDomainDefPtr def,
                         goto error;
                     }
 
-                    if (VIR_ALLOC_N(disk->driverType, (offset-src)+1)< 0)
+                    if (!(driverType = strndup(src, offset - src)))
                         goto no_memory;
-                    if (virStrncpy(disk->driverType, src, offset-src,
-                                   (offset-src)+1) == NULL) {
+                    if (STREQ(driverType, "aio"))
+                        disk->format = VIR_STORAGE_FILE_RAW;
+                    else
+                        disk->format =
+                            virStorageFileFormatTypeFromString(driverType);
+                    VIR_FREE(driverType);
+                    if (disk->format <= 0) {
                         virReportError(VIR_ERR_INTERNAL_ERROR,
-                                       _("Driver type %s too big for destination"),
-                                       src);
+                                       _("Unknown driver type %s"), src);
                         goto error;
                     }
-                    if (STREQ(disk->driverType, "aio")) {
-                        /* In-place conversion to "raw" */
-                        disk->driverType[0] = 'r';
-                        disk->driverType[1] = 'a';
-                        disk->driverType[2] = 'w';
-                    }
 
                     src = offset + 1;
                     /* Its possible to use blktap driver for block devs
@@ -1837,9 +1838,12 @@ xenFormatSxprDisk(virDomainDiskDefPtr def,
         if (def->driverName) {
             if (STREQ(def->driverName, "tap") ||
                 STREQ(def->driverName, "tap2")) {
-                const char *type = def->driverType ? def->driverType : "aio";
-                if (STREQ(type, "raw"))
+                const char *type;
+
+                if (!def->format || def->format == VIR_STORAGE_FILE_RAW)
                     type = "aio";
+                else
+                    type = virStorageFileFormatTypeToString(def->format);
                 virBufferEscapeSexpr(buf, "(uname '%s:", def->driverName);
                 virBufferEscapeSexpr(buf, "%s:", type);
                 virBufferEscapeSexpr(buf, "%s')", def->src);
diff --git a/src/xenxs/xen_xm.c b/src/xenxs/xen_xm.c
index c564d35fbd..2e560a65ae 100644
--- a/src/xenxs/xen_xm.c
+++ b/src/xenxs/xen_xm.c
@@ -37,6 +37,7 @@
 #include "xen_xm.h"
 #include "xen_sxpr.h"
 #include "domain_conf.h"
+#include "storage_file.h"
 
 /* Convenience method to grab a long int from the config file object */
 static int xenXMConfigGetBool(virConfPtr conf,
@@ -554,24 +555,25 @@ xenParseXM(virConfPtr conf, int xendConfigVersion,
                 /* And the sub-type for tap:XXX: type */
                 if (disk->driverName &&
                     STREQ(disk->driverName, "tap")) {
+                    char *driverType;
+
                     if (!(tmp = strchr(disk->src, ':')))
                         goto skipdisk;
-                    if (VIR_ALLOC_N(disk->driverType, (tmp - disk->src) + 1) < 0)
+
+                    if (!(driverType = strndup(disk->src, tmp - disk->src)))
                         goto no_memory;
-                    if (virStrncpy(disk->driverType, disk->src,
-                                   (tmp - disk->src),
-                                   (tmp - disk->src) + 1) == NULL) {
+                    if (STREQ(driverType, "aio"))
+                        disk->format = VIR_STORAGE_FILE_RAW;
+                    else
+                        disk->format =
+                            virStorageFileFormatTypeFromString(driverType);
+                    VIR_FREE(driverType);
+                    if (disk->format <= 0) {
                         virReportError(VIR_ERR_INTERNAL_ERROR,
-                                       _("Driver type %s too big for destination"),
+                                       _("Unknown driver type %s"),
                                        disk->src);
                         goto cleanup;
                     }
-                    if (STREQ(disk->driverType, "aio")) {
-                        /* In-place conversion to "raw" */
-                        disk->driverType[0] = 'r';
-                        disk->driverType[1] = 'a';
-                        disk->driverType[2] = 'w';
-                    }
 
                     /* Strip the prefix we found off the source file name */
                     memmove(disk->src, disk->src+(tmp-disk->src)+1,
@@ -1208,10 +1210,13 @@ static int xenFormatXMDisk(virConfValuePtr list,
     virConfValuePtr val, tmp;
 
     if(disk->src) {
-        if (disk->driverName) {
-            const char *type = disk->driverType ? disk->driverType : "aio";
-            if (STREQ(type, "raw"))
+        if (disk->format) {
+            const char *type;
+
+            if (disk->format == VIR_STORAGE_FILE_RAW)
                 type = "aio";
+            else
+                type = virStorageFileFormatTypeToString(disk->format);
             virBufferAsprintf(&buf, "%s:", disk->driverName);
             if (STREQ(disk->driverName, "tap"))
                 virBufferAsprintf(&buf, "%s:", type);