diff --git a/backend/controllers/logs.go b/backend/controllers/logs.go
index 2d2c6ae..600d59e 100644
--- a/backend/controllers/logs.go
+++ b/backend/controllers/logs.go
@@ -386,7 +386,7 @@ func (ctrl *LogsController) Stats(c *gin.Context) {
 		utils.Forbidden(c, err.Error())
 		return
 	}
-	st, err := services.LokiStatsFor(c.Request.Context(), src, query, req.Start, req.End)
+	st, err := services.LokiStatsCached(c.Request.Context(), src, query, req.Start, req.End)
 	if err != nil {
 		// Loki 的 index/stats 只支持标签选择器。查询里带 `|= "error"` 这类行过滤时
 		// Loki 回 400 "only label matchers are supported"，原来被包装成 502
diff --git a/backend/services/daily_volume.go b/backend/services/daily_volume.go
index dc38056..aa50f01 100644
--- a/backend/services/daily_volume.go
+++ b/backend/services/daily_volume.go
@@ -3,7 +3,6 @@ package services
 import (
 	"context"
 	"log"
-	"sort"
 	"time"
 
 	"lokistack/models"
@@ -19,6 +18,10 @@ type DailyVolumePoint struct {
 	Partial bool `json:"partial"`
 	// FromHistory true=来自平台留存历史；false=刚从 Loki 实时查的
 	FromHistory bool `json:"fromHistory"`
+	// Missing 该天平台没有抓到快照（超过留存期/平台当天没运行）。
+	// 必须和"当天日志量真的是 0"区分开：前者是"不知道"，后者是"确实没日志"。
+	// 否则 30/90/365 天的图上会出现大片 0，被误读成"日志量暴跌"。
+	Missing bool `json:"missing"`
 }
 
 const (
@@ -216,30 +219,38 @@ func GetDailyVolumeHistory(sourceID uint, days int) []DailyVolumePoint {
 	// 而且这条重查询还和页面的 histogram/stats 抢 Loki，导致那两个接口同时 502。
 	// 当天那根柱子由后台定时任务（每 30 分钟）补，慢几分钟完全可接受。
 
-	from := dateKey(time.Now().AddDate(0, 0, -(days - 1)))
-	points := []DailyVolumePoint{}
+	// 始终返回 days 个点（缺失的那天标 Missing）。
+	// 之前只返回"已抓到的快照"，于是 7/30/90/365 全都返回同样 4 个点，
+	// 用户切范围看不到任何变化，以为"切换没反应"。
+	now := time.Now()
+	byDate := map[string]models.DailyVolumeSnapshot{}
 	db := repository.GetDB()
-	if db == nil {
-		return points
+	if db != nil {
+		db.RLock()
+		for _, snap := range db.DailyVolumeSnapshots {
+			if snap.SourceID != sourceID || snap.Namespace != "" {
+				continue
+			}
+			byDate[snap.Date] = snap
+		}
+		db.RUnlock()
 	}
-	db.RLock()
-	defer db.RUnlock()
-	for _, snap := range db.DailyVolumeSnapshots {
-		if snap.SourceID != sourceID || snap.Namespace != "" {
+
+	points := make([]DailyVolumePoint, 0, days)
+	for i := days - 1; i >= 0; i-- {
+		date := dateKey(now.AddDate(0, 0, -i))
+		if snap, ok := byDate[date]; ok {
+			points = append(points, DailyVolumePoint{
+				Date:        snap.Date,
+				Bytes:       snap.Bytes,
+				Entries:     snap.Entries,
+				Partial:     snap.Partial,
+				FromHistory: true,
+			})
 			continue
 		}
-		if snap.Date < from {
-			continue
-		}
-		points = append(points, DailyVolumePoint{
-			Date:        snap.Date,
-			Bytes:       snap.Bytes,
-			Entries:     snap.Entries,
-			Partial:     snap.Partial,
-			FromHistory: true,
-		})
+		points = append(points, DailyVolumePoint{Date: date, Missing: true, FromHistory: true})
 	}
-	sort.Slice(points, func(i, j int) bool { return points[i].Date < points[j].Date })
 	return points
 }
 
diff --git a/backend/services/log_query.go b/backend/services/log_query.go
index 33e0348..a6e0137 100644
--- a/backend/services/log_query.go
+++ b/backend/services/log_query.go
@@ -701,6 +701,61 @@ func LokiMetrics(ctx context.Context, src *models.LogSource, query string, start
 	return series, nil
 }
 
+// ── 总条数/总体积的短缓存 ─────────────────────────────────────────────
+// /logs/stats 走 index/stats，实测 5 分钟窗口要 1.2 秒（60 分钟更慢）。
+// 分析页每次进页面、每次切时间范围都会打它，而这类聚合值的可容忍陈旧度
+// 与指标查询一致（分钟级），所以用同样的 90s TTL + 2 分钟取整。
+const (
+	statsCacheTTL = 90 * time.Second
+	statsCacheMax = 200
+)
+
+type statsCacheEntry struct {
+	stats     *LokiStats
+	expiresAt time.Time
+}
+
+var (
+	statsCacheMu sync.Mutex
+	statsCache   = map[string]statsCacheEntry{}
+)
+
+// LokiStatsCached 带短缓存的总量统计。
+func LokiStatsCached(ctx context.Context, src *models.LogSource, query string, start, end int64) (*LokiStats, error) {
+	key := ""
+	if src != nil {
+		bucket := int64(metricCacheBucket)
+		key = fmt.Sprintf("%d|%s|%d|%d", src.ID, query, start/bucket, end/bucket)
+		statsCacheMu.Lock()
+		if entry, ok := statsCache[key]; ok && time.Now().Before(entry.expiresAt) {
+			statsCacheMu.Unlock()
+			return entry.stats, nil
+		}
+		statsCacheMu.Unlock()
+	}
+
+	st, err := LokiStatsFor(ctx, src, query, start, end)
+	if err != nil || key == "" {
+		return st, err
+	}
+
+	statsCacheMu.Lock()
+	if len(statsCache) >= statsCacheMax {
+		now := time.Now()
+		for k, v := range statsCache {
+			if now.After(v.expiresAt) {
+				delete(statsCache, k)
+			}
+		}
+		if len(statsCache) >= statsCacheMax {
+			statsCache = map[string]statsCacheEntry{}
+		}
+	}
+	statsCache[key] = statsCacheEntry{stats: st, expiresAt: time.Now().Add(statsCacheTTL)}
+	statsCacheMu.Unlock()
+	return st, nil
+}
+
 // lokiMetricsUncached 真正打 Loki 的实现（不带缓存）。
 func lokiMetricsUncached(ctx context.Context, src *models.LogSource, query string, start, end int64) ([]MetricSeries, error) {
 	if end <= 0 {
diff --git a/frontend/src/api/logs/index.ts b/frontend/src/api/logs/index.ts
index de35bcc..f342cb7 100644
--- a/frontend/src/api/logs/index.ts
+++ b/frontend/src/api/logs/index.ts
@@ -26,6 +26,8 @@ export interface DailyVolumePoint {
   entries: number
   /** 当天未结束或抓取时数据不全 */
   partial: boolean
+  /** 该天平台没有留存快照（超过留存期/当天平台没运行）——与"日志量真的是 0"不同 */
+  missing?: boolean
 }
 export const logsApi = {
   sources: () => http.get<PageData<LogSource>>('/logs/sources'),
diff --git a/frontend/src/i18n/locales/en/analysis.ts b/frontend/src/i18n/locales/en/analysis.ts
index 027bc84..806ac41 100644
--- a/frontend/src/i18n/locales/en/analysis.ts
+++ b/frontend/src/i18n/locales/en/analysis.ts
@@ -52,6 +52,8 @@ export default {
     other: 'Other',
   },
   daily: {
+    notRetained: 'Not retained',
+    missingHint: '{{count}} day(s) have no retained snapshot (grey bars) — that does NOT mean zero logs on those days.',
     fixedBadge: 'Platform history',
     badge: 'Platform history',
     title: 'Daily volume',
diff --git a/frontend/src/i18n/locales/zh/analysis.ts b/frontend/src/i18n/locales/zh/analysis.ts
index 902947d..1cdfa64 100644
--- a/frontend/src/i18n/locales/zh/analysis.ts
+++ b/frontend/src/i18n/locales/zh/analysis.ts
@@ -52,6 +52,8 @@ export default {
     other: '其他',
   },
   daily: {
+    notRetained: '未留存',
+    missingHint: '其中 {{count}} 天平台没有留存记录（灰色柱），不是"当天没有日志"。',
     fixedBadge: '平台留存历史',
     badge: '平台留存历史',
     title: '每日日志量',
diff --git a/frontend/src/pages/analysis/components/DailyVolumeChart.tsx b/frontend/src/pages/analysis/components/DailyVolumeChart.tsx
index aa38ace..b69b009 100644
--- a/frontend/src/pages/analysis/components/DailyVolumeChart.tsx
+++ b/frontend/src/pages/analysis/components/DailyVolumeChart.tsx
@@ -29,10 +29,15 @@ export const DailyVolumeChart = memo(function DailyVolumeChart({ points, days, o
     bytes: point.bytes,
     entries: point.entries,
     partial: point.partial,
+    missing: Boolean(point.missing),
   })), [points])
 
-  const hasData = data.some(item => item.bytes > 0)
-  const coverage = points.length
+  // 有留存的天数与"完全没留存"的天数分开统计：
+  // 后者是"不知道"，不能画成 0 让人以为那天没日志。
+  const covered = data.filter(item => !item.missing)
+  const missingCount = data.length - covered.length
+  const hasData = covered.some(item => item.bytes > 0)
+  const coverage = covered.length
 
   return (
     <div className="space-y-3">
@@ -68,8 +73,9 @@ export const DailyVolumeChart = memo(function DailyVolumeChart({ points, days, o
               <YAxis tick={{ fontSize: 11 }} width={64} tickFormatter={(value: number) => formatBytes(value)} />
               <Tooltip
                 formatter={(value: number, _name, item) => {
-                  const partial = (item?.payload as { partial?: boolean } | undefined)?.partial
-                  return [`${formatBytes(value)}${partial ? ` · ${t('daily.inProgress')}` : ''}`, t('daily.seriesVolume')]
+                  const payload = item?.payload as { partial?: boolean; missing?: boolean } | undefined
+                  if (payload?.missing) return [t('daily.notRetained'), t('daily.seriesVolume')]
+                  return [`${formatBytes(value)}${payload?.partial ? ` · ${t('daily.inProgress')}` : ''}`, t('daily.seriesVolume')]
                 }}
               />
               {/* 圆柱形柱子：顶部圆角 + 渐变，当天未结束的用空心区分 */}
@@ -77,7 +83,13 @@ export const DailyVolumeChart = memo(function DailyVolumeChart({ points, days, o
                 {data.map(item => (
                   <Cell
                     key={item.date}
-                    fill={item.partial ? 'hsl(var(--info) / 0.35)' : 'url(#dailyVolumeBar)'}
+                    fill={
+                      item.missing
+                        ? 'hsl(var(--muted-foreground) / 0.12)'
+                        : item.partial
+                          ? 'hsl(var(--info) / 0.35)'
+                          : 'url(#dailyVolumeBar)'
+                    }
                     stroke={item.partial ? 'hsl(var(--info))' : undefined}
                     strokeDasharray={item.partial ? '3 3' : undefined}
                   />
@@ -89,6 +101,14 @@ export const DailyVolumeChart = memo(function DailyVolumeChart({ points, days, o
       ) : (
         <EmptyChart message={t('daily.empty')} />
       )}
+
+      {/* 灰柱 = 平台没有留存那天（不是"日志量为 0"），必须显式说明，
+          否则 30/90/365 天视角下会被误读成"以前日志很少" */}
+      {missingCount > 0 && (
+        <p className="text-[11px] text-muted-foreground">
+          {t('daily.missingHint', { count: missingCount })}
+        </p>
+      )}
     </div>
   )
 })