diff --git a/lib/datastruct/hash.c b/lib/datastruct/hash.c
index 002ff7fbb..b9c292062 100644
--- a/lib/datastruct/hash.c
+++ b/lib/datastruct/hash.c
@@ -181,6 +181,22 @@ void hash_iterate(struct hash_table *t, iterate_fn f)
 			f(c->data);
 }
 
+void hash_wipe(struct hash_table *t)
+{
+	struct hash_node **c, *old;
+	int i;
+
+	for (i = 0; i < t->num_slots; i++) {
+		c = &t->slots[i];
+		while (*c) {
+			old = *c;
+			*c = (*c)->next;
+			dbg_free(old);
+			t->num_nodes--;
+		}
+	}
+}
+
 char *hash_get_key(struct hash_table *t, struct hash_node *n)
 {
 	return n->key;
diff --git a/lib/datastruct/hash.h b/lib/datastruct/hash.h
index bd0c4eba2..d611ca9b0 100644
--- a/lib/datastruct/hash.h
+++ b/lib/datastruct/hash.h
@@ -14,6 +14,7 @@ typedef void (*iterate_fn)(void *data);
 
 struct hash_table *hash_create(unsigned size_hint);
 void hash_destroy(struct hash_table *t);
+void hash_wipe(struct hash_table *t);
 
 void *hash_lookup(struct hash_table *t, const char *key);
 int hash_insert(struct hash_table *t, const char *key, void *data);
diff --git a/lib/filters/filter-persistent.c b/lib/filters/filter-persistent.c
index 4f7cef869..9750b398d 100644
--- a/lib/filters/filter-persistent.c
+++ b/lib/filters/filter-persistent.c
@@ -42,8 +42,8 @@ int persistent_filter_wipe(struct dev_filter *f)
 {
 	struct pfilter *pf = (struct pfilter *) f->private;
 
-	hash_destroy(pf->devices);
-	return _init_hash(pf);
+	hash_wipe(pf->devices);
+	return 1;
 }
 
 static int _read_array(struct pfilter *pf, struct config_file *cf,
@@ -53,8 +53,8 @@ static int _read_array(struct pfilter *pf, struct config_file *cf,
 	struct config_value *cv;
 
 	if (!(cn = find_config_node(cf->root, path, '/'))) {
-		log_verbose("Couldn't find 'valid_devices' array in '%s'",
-			 pf->file);
+		log_very_verbose("Couldn't find %s array in '%s'",
+			 path, pf->file);
 		return 0;
 	}
 
@@ -64,7 +64,7 @@ static int _read_array(struct pfilter *pf, struct config_file *cf,
 	 */
 	for (cv = cn->v; cv; cv = cv->next) {
 		if (cv->type != CFG_STRING) {
-			log_verbose("Valid_devices array contains a value "
+			log_verbose("Devices array contains a value "
 				 "which is not a string ... ignoring");
 			continue;
 		}
@@ -93,8 +93,10 @@ int persistent_filter_load(struct dev_filter *f)
 		goto out;
 	}
 
-	if (_read_array(pf, cf, "/valid_devices", PF_GOOD_DEVICE) &&
-	    _read_array(pf, cf, "/invalid_devices", PF_BAD_DEVICE))
+	_read_array(pf, cf, "persistent_filter_cache/valid_devices", PF_GOOD_DEVICE);
+	_read_array(pf, cf, "persistent_filter_cache/invalid_devices", PF_BAD_DEVICE);
+
+	if (hash_get_num_entries(pf->devices))
 		r = 1;
 
  out:
@@ -109,8 +111,7 @@ static void _write_array(struct pfilter *pf, FILE *fp, const char *path,
 	int first = 1;
 	struct hash_node *n;
 
-	fprintf(fp, "%s=[\n", path);
-	for (n = hash_get_first(pf->devices); n;
+	for (n = hash_get_first(pf->devices); n; 
 	     n = hash_get_next(pf->devices, n)) {
 		d = hash_get_data(pf->devices, n);
 
@@ -119,13 +120,18 @@ static void _write_array(struct pfilter *pf, FILE *fp, const char *path,
 
 		if (!first)
 			fprintf(fp, ",\n");
-		else
+		else {
+			fprintf(fp, "\t%s=[\n", path);
 			first = 0;
+		}
 
-		fprintf(fp, "\t\"%s\"", hash_get_key(pf->devices, n));
+		fprintf(fp, "\t\t\"%s\"", hash_get_key(pf->devices, n));
 	}
 
-	fprintf(fp, "\n]\n");
+	if (!first)
+		fprintf(fp, "\n\t]\n");
+
+	return;
 }
 
 int persistent_filter_dump(struct dev_filter *f)
@@ -143,10 +149,12 @@ int persistent_filter_dump(struct dev_filter *f)
 	}
 
 	fprintf(fp, "# This file is automatically maintained by lvm.\n\n");
+	fprintf(fp, "persistent_filter_cache {\n");
 
 	_write_array(pf, fp, "valid_devices", PF_GOOD_DEVICE);
 	_write_array(pf, fp, "invalid_devices", PF_BAD_DEVICE);
 
+	fprintf(fp, "}\n");
 	fclose(fp);
 	return 1;
 }
diff --git a/tools/lvm.c b/tools/lvm.c
index fbfd0e2ac..926922d3c 100644
--- a/tools/lvm.c
+++ b/tools/lvm.c
@@ -49,6 +49,8 @@ static struct command *_commands;
 struct io_space *ios;
 
 static struct dev_filter *_filter;
+/* Whether or not to dump persistent filter state */
+static int dump_filter;
 static struct config_file *_cf;
 
 static int _interactive;
@@ -642,6 +644,8 @@ static struct dev_filter *filter_setup(void)
 	struct dev_filter *f3, *f4;
 	struct stat st;
 
+	dump_filter = 0;
+
 	if (!(f3 = filter_components_setup()))
 		return 0;
 
@@ -650,9 +654,13 @@ static struct dev_filter *filter_setup(void)
 
 	if (!(f4 = persistent_filter_create(f3, lvm_cache))) {
 		log_error("Failed to create persistent device filter");
-		return f3;
+		return 0;
 	}
 
+	/* Should we ever dump persistent filter state? */
+	if (find_config_int(_cf->root, "devices/write_cache_state", '/', 1))
+		dump_filter = 1;
+	
 	if (!stat(lvm_cache, &st) && !persistent_filter_load(f4))
 		log_verbose("Failed to load existing device cache from %s",
 			    lvm_cache);
@@ -728,6 +736,9 @@ static void __fin_commands(void)
 
 static void fin(void)
 {
+	if (dump_filter)
+		persistent_filter_dump(_filter);
+
 	ios->destroy(ios);
 	_filter->destroy(_filter);
 	dev_cache_exit();
diff --git a/tools/pvscan.c b/tools/pvscan.c
index 6e1cb4878..7adc59f6e 100644
--- a/tools/pvscan.c
+++ b/tools/pvscan.c
@@ -53,8 +53,10 @@ int pvscan(int argc, char **argv)
 			  arg_count(exported_ARG) ?
 			  "of exported volume group(s)" : "in no volume group");
 
-	log_verbose("Walking through all physical volumes");
+	log_verbose("Wiping cache of LVM-capable devices");
+	persistent_filter_wipe(ios->filter);
 
+	log_verbose("Walking through all physical volumes");
 	if (!(pvs = ios->get_pvs(ios)))
 		return ECMD_FAILED;
 
diff --git a/tools/vgscan.c b/tools/vgscan.c
index f8cf53066..a205be71f 100644
--- a/tools/vgscan.c
+++ b/tools/vgscan.c
@@ -29,6 +29,9 @@ int vgscan(int argc, char **argv)
 		return EINVALID_CMD_LINE;
 	}
 
+        log_verbose("Wiping cache of LVM-capable devices");
+        persistent_filter_wipe(ios->filter);
+
 	log_print("Reading all physical volumes (this may take a while...)");
 
 	return process_each_vg(argc, argv, &vgscan_single);