diff --git a/lib/Makefile.in b/lib/Makefile.in
index 0fb07dbff..89802ae45 100644
--- a/lib/Makefile.in
+++ b/lib/Makefile.in
@@ -14,6 +14,7 @@ SOURCES=\
 	device/dev-cache.c \
 	device/dev-io.c \
 	device/device.c \
+	display/display.c \
 	filters/filter.c \
 	format1/disk-rep.c \
 	format1/format1.c \
diff --git a/lib/format1/disk-rep.h b/lib/format1/disk-rep.h
index 528c08220..0f7589d02 100644
--- a/lib/format1/disk-rep.h
+++ b/lib/format1/disk-rep.h
@@ -18,6 +18,10 @@
 #define MAX_LV 256
 #define MAX_VG 99
 
+#define MIN_PE_SIZE ( 8192L / SECTOR_SIZE)     /* 8 KB in sectors */
+#define MAX_PE_SIZE ( 16L * 1024L * 1024L / SECTOR_SIZE * 1024)
+#define PE_SIZE_PV_SIZE_REL 5   /* PV size must be at least 5 times PE size */
+
 #define UNMAPPED_EXTENT 0
 
 /* volume group */
diff --git a/lib/format1/format1.c b/lib/format1/format1.c
index 1f3afe729..422e86dc7 100644
--- a/lib/format1/format1.c
+++ b/lib/format1/format1.c
@@ -10,6 +10,7 @@
 #include "hash.h"
 #include "list.h"
 #include "log.h"
+#include "display.h"
 
 static int _check_vgs(struct list_head *pvs)
 {
@@ -388,6 +389,32 @@ int _vg_setup(struct io_space *is, struct volume_group *vg)
         if (vg->max_pv >= MAX_PV)
 		vg->max_pv = MAX_PV - 1;
 
+	if (vg->extent_size > MAX_PE_SIZE || vg->extent_size < MIN_PE_SIZE) {
+		char *dummy, *dummy2;
+
+		log_error("Extent size must be between %s and %s",
+			(dummy = display_size(MIN_PE_SIZE / 2, SIZE_SHORT)), 
+			(dummy2 = display_size(MAX_PE_SIZE / 2, SIZE_SHORT)));
+
+		dbg_free(dummy);
+		dbg_free(dummy2);
+		return 0;
+	}
+
+	if (vg->extent_size % MIN_PE_SIZE) {
+		char *dummy;
+		log_error("Extent size must be multiple of %s",
+			(dummy = display_size(MIN_PE_SIZE / 2, SIZE_SHORT)));
+		dbg_free(dummy);
+		return 0;
+	}
+
+	/* Redundant? */
+	if (vg->extent_size & (vg->extent_size - 1)) {
+		log_error("Extent size must be power of 2");
+		return 0;
+	}
+
 	return 1;
 }
 
diff --git a/lib/format1/layout.c b/lib/format1/layout.c
index 5851a0255..1168fbea6 100644
--- a/lib/format1/layout.c
+++ b/lib/format1/layout.c
@@ -106,6 +106,12 @@ int calculate_extent_count(struct physical_volume *pv)
 	 */
 	pvd->pe_total = (pv->size / pv->pe_size);
 
+	if (pvd->pe_total < PE_SIZE_PV_SIZE_REL) {
+		log_error("Insufficient space for extents on %s",
+			  pv->dev->name);
+		return 0;
+	}
+
 	do {
 		pvd->pe_total--;
 		_calc_simple_layout(pvd);
diff --git a/lib/metadata/metadata.c b/lib/metadata/metadata.c
index d2642e4c1..7f636c9f1 100644
--- a/lib/metadata/metadata.c
+++ b/lib/metadata/metadata.c
@@ -52,11 +52,13 @@ int _add_pv_to_vg(struct io_space *ios, struct volume_group *vg,
 	/* FIXME Tie this to activation or not? */
 	pv->status |= ACTIVE;
 
+	/* Units of 512-byte sectors */
 	if (!dev_get_size(pv->dev, &pv->size)) {
 		stack;
 		return 0;
 	}
 
+	/* Units of 512-byte sectors */
 	pv->pe_size = vg->extent_size;
 
 	/*
@@ -69,7 +71,7 @@ int _add_pv_to_vg(struct io_space *ios, struct volume_group *vg,
 	pv->pe_allocated = 0;
 
 	if (!ios->pv_setup(ios, pv, vg)) {
-		log_debug("Format specific setup of physical volume '%s' "
+		log_debug("Format-specific setup of physical volume '%s' "
 			  "failed.", pv_name);
 		return 0;
 	}
diff --git a/tools/vgcreate.c b/tools/vgcreate.c
index 5ff143bd2..3f57e4204 100644
--- a/tools/vgcreate.c
+++ b/tools/vgcreate.c
@@ -9,7 +9,8 @@
 /* FIXME From config file? */
 #define DEFAULT_PV 255
 #define DEFAULT_LV 255
-#define DEFAULT_EXTENT 8192
+
+#define DEFAULT_EXTENT 4096  /* In KB */
 
 int vgcreate(int argc, char **argv)
 {
@@ -31,7 +32,9 @@ int vgcreate(int argc, char **argv)
 	vg_name = argv[0];
 	max_lv = arg_int_value(maxlogicalvolumes_ARG, DEFAULT_LV);
 	max_pv = arg_int_value(maxphysicalvolumes_ARG, DEFAULT_PV);
-	extent_size = arg_int_value(physicalextentsize_ARG, DEFAULT_EXTENT);
+
+	/* Units of 512-byte sectors */
+	extent_size = arg_int_value(physicalextentsize_ARG, DEFAULT_EXTENT) * 2;
 
 	if (max_lv < 1) {
 		log_error("maxlogicalvolumes too low");