diff --git a/include/sys/vdev_impl.h b/include/sys/vdev_impl.h
index 1df61a587d6c..8862d9bc9854 100644
--- a/include/sys/vdev_impl.h
+++ b/include/sys/vdev_impl.h
@@ -49,6 +49,7 @@ extern "C" {
  * Forward declarations that lots of things need.
  */
 typedef struct vdev_queue vdev_queue_t;
+typedef struct vdev_io vdev_io_t;
 typedef struct vdev_cache vdev_cache_t;
 typedef struct vdev_cache_entry vdev_cache_entry_t;
 
@@ -102,9 +103,15 @@ struct vdev_queue {
 	avl_tree_t	vq_read_tree;
 	avl_tree_t	vq_write_tree;
 	avl_tree_t	vq_pending_tree;
+	list_t		vq_io_list;
 	kmutex_t	vq_lock;
 };
 
+struct vdev_io {
+	char		vi_buffer[SPA_MAXBLOCKSIZE]; /* Must be first */
+	list_node_t	vi_node;
+};
+
 /*
  * Virtual device descriptor
  */
diff --git a/include/sys/zio.h b/include/sys/zio.h
index c0da4e2d78cd..4f20cab6591e 100644
--- a/include/sys/zio.h
+++ b/include/sys/zio.h
@@ -494,6 +494,8 @@ extern void *zio_buf_alloc(size_t size);
 extern void zio_buf_free(void *buf, size_t size);
 extern void *zio_data_buf_alloc(size_t size);
 extern void zio_data_buf_free(void *buf, size_t size);
+extern void *zio_vdev_alloc(void);
+extern void zio_vdev_free(void *buf);
 
 extern void zio_resubmit_stage_async(void *);
 
diff --git a/module/zfs/vdev_queue.c b/module/zfs/vdev_queue.c
index aacc55c49f4e..7ba638952e10 100644
--- a/module/zfs/vdev_queue.c
+++ b/module/zfs/vdev_queue.c
@@ -106,6 +106,7 @@ void
 vdev_queue_init(vdev_t *vd)
 {
 	vdev_queue_t *vq = &vd->vdev_queue;
+	int i;
 
 	mutex_init(&vq->vq_lock, NULL, MUTEX_DEFAULT, NULL);
 
@@ -120,18 +121,36 @@ vdev_queue_init(vdev_t *vd)
 
 	avl_create(&vq->vq_pending_tree, vdev_queue_offset_compare,
 	    sizeof (zio_t), offsetof(struct zio, io_offset_node));
+
+	/*
+	 * A list of buffers which can be used for aggregate I/O, this
+	 * avoids the need to allocate them on demand when memory is low.
+	 */
+	list_create(&vq->vq_io_list, sizeof (vdev_io_t),
+	    offsetof(vdev_io_t, vi_node));
+
+	for (i = 0; i < zfs_vdev_max_pending; i++)
+		list_insert_tail(&vq->vq_io_list, zio_vdev_alloc());
 }
 
 void
 vdev_queue_fini(vdev_t *vd)
 {
 	vdev_queue_t *vq = &vd->vdev_queue;
+	vdev_io_t *vi;
 
 	avl_destroy(&vq->vq_deadline_tree);
 	avl_destroy(&vq->vq_read_tree);
 	avl_destroy(&vq->vq_write_tree);
 	avl_destroy(&vq->vq_pending_tree);
 
+	while ((vi = list_head(&vq->vq_io_list)) != NULL) {
+		list_remove(&vq->vq_io_list, vi);
+		zio_vdev_free(vi);
+	}
+
+	list_destroy(&vq->vq_io_list);
+
 	mutex_destroy(&vq->vq_lock);
 }
 
@@ -152,6 +171,8 @@ vdev_queue_io_remove(vdev_queue_t *vq, zio_t *zio)
 static void
 vdev_queue_agg_io_done(zio_t *aio)
 {
+	vdev_queue_t *vq = &aio->io_vd->vdev_queue;
+	vdev_io_t *vi = aio->io_data;
 	zio_t *pio;
 
 	while ((pio = zio_walk_parents(aio)) != NULL)
@@ -159,7 +180,9 @@ vdev_queue_agg_io_done(zio_t *aio)
 			bcopy((char *)aio->io_data + (pio->io_offset -
 			    aio->io_offset), pio->io_data, pio->io_size);
 
-	zio_buf_free(aio->io_data, aio->io_size);
+	mutex_enter(&vq->vq_lock);
+	list_insert_tail(&vq->vq_io_list, vi);
+	mutex_exit(&vq->vq_lock);
 }
 
 /*
@@ -176,6 +199,7 @@ vdev_queue_io_to_issue(vdev_queue_t *vq, uint64_t pending_limit)
 {
 	zio_t *fio, *lio, *aio, *dio, *nio, *mio;
 	avl_tree_t *t;
+	vdev_io_t *vi;
 	int flags;
 	uint64_t maxspan = zfs_vdev_aggregation_limit;
 	uint64_t maxgap;
@@ -194,6 +218,12 @@ vdev_queue_io_to_issue(vdev_queue_t *vq, uint64_t pending_limit)
 	flags = fio->io_flags & ZIO_FLAG_AGG_INHERIT;
 	maxgap = (t == &vq->vq_read_tree) ? zfs_vdev_read_gap_limit : 0;
 
+	vi = list_head(&vq->vq_io_list);
+	if (vi == NULL) {
+		vi = zio_vdev_alloc();
+		list_insert_head(&vq->vq_io_list, vi);
+	}
+
 	if (!(flags & ZIO_FLAG_DONT_AGGREGATE)) {
 		/*
 		 * We can aggregate I/Os that are sufficiently adjacent and of
@@ -283,9 +313,10 @@ vdev_queue_io_to_issue(vdev_queue_t *vq, uint64_t pending_limit)
 	if (fio != lio) {
 		uint64_t size = IO_SPAN(fio, lio);
 		ASSERT(size <= zfs_vdev_aggregation_limit);
+		ASSERT(vi != NULL);
 
 		aio = zio_vdev_delegated_io(fio->io_vd, fio->io_offset,
-		    zio_buf_alloc(size), size, fio->io_type, ZIO_PRIORITY_AGG,
+		    vi, size, fio->io_type, ZIO_PRIORITY_AGG,
 		    flags | ZIO_FLAG_DONT_CACHE | ZIO_FLAG_DONT_QUEUE,
 		    vdev_queue_agg_io_done, NULL);
 
@@ -313,6 +344,7 @@ vdev_queue_io_to_issue(vdev_queue_t *vq, uint64_t pending_limit)
 		} while (dio != lio);
 
 		avl_add(&vq->vq_pending_tree, aio);
+		list_remove(&vq->vq_io_list, vi);
 
 		return (aio);
 	}
diff --git a/module/zfs/zio.c b/module/zfs/zio.c
index 206ed9a936c3..fe2bdc867fea 100644
--- a/module/zfs/zio.c
+++ b/module/zfs/zio.c
@@ -73,6 +73,7 @@ char *zio_type_name[ZIO_TYPES] = {
  */
 kmem_cache_t *zio_cache;
 kmem_cache_t *zio_link_cache;
+kmem_cache_t *zio_vdev_cache;
 kmem_cache_t *zio_buf_cache[SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT];
 kmem_cache_t *zio_data_buf_cache[SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT];
 int zio_bulk_flags = 0;
@@ -141,6 +142,8 @@ zio_init(void)
 	    zio_cons, zio_dest, NULL, NULL, NULL, KMC_KMEM);
 	zio_link_cache = kmem_cache_create("zio_link_cache",
 	    sizeof (zio_link_t), 0, NULL, NULL, NULL, NULL, NULL, KMC_KMEM);
+	zio_vdev_cache = kmem_cache_create("zio_vdev_cache", sizeof(vdev_io_t),
+	    PAGESIZE, NULL, NULL, NULL, NULL, NULL, KMC_VMEM);
 
 	/*
 	 * For small buffers, we want a cache for each multiple of
@@ -230,6 +233,7 @@ zio_fini(void)
 		zio_data_buf_cache[c] = NULL;
 	}
 
+	kmem_cache_destroy(zio_vdev_cache);
 	kmem_cache_destroy(zio_link_cache);
 	kmem_cache_destroy(zio_cache);
 
@@ -294,6 +298,24 @@ zio_data_buf_free(void *buf, size_t size)
 	kmem_cache_free(zio_data_buf_cache[c], buf);
 }
 
+/*
+ * Dedicated I/O buffers to ensure that memory fragmentation never prevents
+ * or significantly delays the issuing of a zio.   These buffers are used
+ * to aggregate I/O and could be used for raidz stripes.
+ */
+void *
+zio_vdev_alloc(void)
+{
+	return (kmem_cache_alloc(zio_vdev_cache, KM_PUSHPAGE));
+}
+
+void
+zio_vdev_free(void *buf)
+{
+	kmem_cache_free(zio_vdev_cache, buf);
+
+}
+
 /*
  * ==========================================================================
  * Push and pop I/O transform buffers