A drive is a drive: NVMe namespaces fold into their controller

An Apple SSD presents three namespaces and the kernel lists each as a whole disk, so the
dashboard was showing one drive as three. The Disks page has always folded them; now the
dashboard, the Top tab and the disk.* sensors do too.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

internal/metrics/metrics.go

@@ -715,10 +715,53 @@ func (c *Collector) disks(dt float64) []Disk {
 		c.prevDisk[name] = [3]uint64{rd, wr, ticks}
 		out = append(out, d)
 	}
+	out = foldNVMe(out)
 	sort.Slice(out, func(i, j int) bool { return out[i].Name < out[j].Name })
 	return out
 }
 
+var nsRe = regexp.MustCompile(`^(nvme\d+)n\d+$`)
+
+// foldNVMe merges nvme0n1, nvme0n2, … into the drive they are: one controller presenting
+// several namespaces, which the kernel lists as whole disks apiece. An Apple SSD shows three —
+// the 466 GiB of storage and two of firmware, a few MiB each — and a page that lists disks was
+// listing all three as separate drives. The Disks page has always folded them (internal/storage
+// does the same); this is what the dashboard, the Top tab and the disk.* sensors read.
+//
+// Rates add up across namespaces. Busy does not: they share one controller, so the time it
+// spent working is the longest of them, never the sum.
+func foldNVMe(devs []Disk) []Disk {
+	byCtrl := map[string]int{}
+	out := devs[:0]
+	for _, d := range devs {
+		m := nsRe.FindStringSubmatch(d.Name)
+		if m == nil {
+			out = append(out, d)
+			continue
+		}
+		ctrl := m[1]
+		if i, ok := byCtrl[ctrl]; ok {
+			out[i].Size += d.Size
+			out[i].ReadBps = round1(out[i].ReadBps + d.ReadBps)
+			out[i].WriteBps = round1(out[i].WriteBps + d.WriteBps)
+			if d.UtilPct > out[i].UtilPct {
+				out[i].UtilPct = d.UtilPct
+			}
+			if out[i].Temp == 0 {
+				out[i].Temp = d.Temp
+			}
+			continue
+		}
+		d.Name = ctrl
+		if mdl := strings.TrimSpace(readStr("/sys/class/nvme/" + ctrl + "/model")); mdl != "" {
+			d.Model = mdl
+		}
+		byCtrl[ctrl] = len(out)
+		out = append(out, d)
+	}
+	return out
+}
+
 // ---- filesystems ----
 
 // Kernel/virtual filesystems that aren't storage. Anything else that's mounted is