zpool iostat tells which rotor vector each vdev is part of.

For the time being, abusing the -k flag (of the previous commit).

cmd/zpool/zpool_main.c

@@ -2803,7 +2803,6 @@ print_iostat_labels(iostat_cbdata_t *cb, unsigned int force_column_width,
 
 		}
 	}
-	printf("\n");
 }
 
 /*
@@ -2874,6 +2873,10 @@ print_iostat_dashes(iostat_cbdata_t *cb, unsigned int force_column_width,
 				    "--------------------");
 		}
 	}
+
+	if (cb->cb_flags & IOS_KIND_M)
+		printf("  ---");
+
 	printf("\n");
 }
 
@@ -2916,10 +2919,14 @@ print_iostat_header_impl(iostat_cbdata_t *cb, unsigned int force_column_width,
 
 
 	print_iostat_labels(cb, force_column_width, iostat_top_labels);
+	printf("\n");
 
 	printf("%-*s", namewidth, title);
 
 	print_iostat_labels(cb, force_column_width, iostat_bottom_labels);
+	if (cb->cb_flags & IOS_KIND_M)
+		printf("  nrv");
+	printf("\n");
 
 	print_iostat_separator_impl(cb, force_column_width);
 }
@@ -3370,6 +3377,8 @@ print_vdev_stats(zpool_handle_t *zhp, const char *name, nvlist_t *oldnv,
 	int ret = 0;
 	uint64_t tdelta;
 	double scale;
+	nvlist_t *nvx;
+	uint64_t nrotor = (uint64_t)-1;
 
 	calcvs = safe_malloc(sizeof (*calcvs));
 
@@ -3452,6 +3461,17 @@ print_vdev_stats(zpool_handle_t *zhp, const char *name, nvlist_t *oldnv,
 		print_iostat_histos(cb, oldnv, newnv, scale, name);
 	}
 
+	if (nvlist_lookup_nvlist(newnv, ZPOOL_CONFIG_VDEV_STATS_EX, &nvx) == 0)
+		nvlist_lookup_uint64(nvx, ZPOOL_CONFIG_VDEV_NROTOR,
+		    &nrotor);
+
+	if (cb->cb_flags & IOS_KIND_M) {
+		if (nrotor != (uint64_t)-1)
+			(void) printf("  %d", (int)nrotor);
+		else
+			(void) printf("  -");
+	}
+
 	if (cb->vcdl != NULL) {
 		char *path;
 		if (nvlist_lookup_string(newnv, ZPOOL_CONFIG_PATH,

include/sys/fs/zfs.h

@@ -598,6 +598,7 @@ typedef struct zpool_rewind_policy {
 
 /* Kind (ssd, file, mix, hdd) (part of vdev_stat_ex_t) */
 #define	ZPOOL_CONFIG_VDEV_KIND		"kind"
+#define	ZPOOL_CONFIG_VDEV_NROTOR	"nrotor"
 
 #define	ZPOOL_CONFIG_WHOLE_DISK		"whole_disk"
 #define	ZPOOL_CONFIG_ERRCOUNT		"error_count"
@@ -902,6 +903,8 @@ typedef struct vdev_stat_ex {
 
 	/* Kind of vdev (ssd, file, mixed, hdd).  Exported as one value. */
 	uint64_t vsx_kind;
+	/* Allocation rotor */
+	uint64_t vsx_nrotor;
 } vdev_stat_ex_t;
 
 /*

module/zfs/vdev.c

@@ -2938,6 +2938,10 @@ vdev_get_stats_ex_impl(vdev_t *vd, vdev_stat_t *vs, vdev_stat_ex_t *vsx)
 			vsx->vsx_kind = VDEV_KIND_MIXED;
 		else
 			vsx->vsx_kind = VDEV_KIND_HDD;
+		if (vd->vdev_mg)
+			vsx->vsx_nrotor = vd->vdev_mg->mg_nrot;
+		else
+			vsx->vsx_nrotor = -1;
 	}
 }
 

module/zfs/vdev_label.c

@@ -346,6 +346,8 @@ vdev_config_generate_stats(vdev_t *vd, nvlist_t *nv)
 
 	fnvlist_add_uint64(nvx, ZPOOL_CONFIG_VDEV_KIND, vsx->vsx_kind);
 
+	fnvlist_add_uint64(nvx, ZPOOL_CONFIG_VDEV_NROTOR, vsx->vsx_nrotor);
+
 	/* Add extended stats nvlist to main nvlist */
 	fnvlist_add_nvlist(nv, ZPOOL_CONFIG_VDEV_STATS_EX, nvx);