diff --git a/crates/io-metrics/src/capacity_metrics.rs b/crates/io-metrics/src/capacity_metrics.rs
index b7118a57b..543b5d4d5 100644
--- a/crates/io-metrics/src/capacity_metrics.rs
+++ b/crates/io-metrics/src/capacity_metrics.rs
@@ -55,6 +55,13 @@ pub fn record_capacity_update_completed(source: &'static str, duration: Duration
     .increment(1);
 }
 
+/// Record a committed capacity reading that is degraded: the refresh behind it
+/// had partial disk failures, so some disks kept last-known values.
+#[inline(always)]
+pub fn record_capacity_degraded_reading(source: &'static str) {
+    counter!("rustfs_capacity_degraded_readings_total", "source" => source).increment(1);
+}
+
 /// Record failed capacity update.
 #[inline(always)]
 pub fn record_capacity_update_failed(source: &'static str) {
diff --git a/crates/object-capacity/src/capacity_manager.rs b/crates/object-capacity/src/capacity_manager.rs
index 850e7a05d..c4c8c49b5 100644
--- a/crates/object-capacity/src/capacity_manager.rs
+++ b/crates/object-capacity/src/capacity_manager.rs
@@ -30,9 +30,9 @@ use rustfs_config::{
     ENV_CAPACITY_WRITE_TRIGGER_DELAY,
 };
 use rustfs_io_metrics::capacity_metrics::{
-    record_capacity_current_bytes, record_capacity_dirty_disk_count, record_capacity_refresh_inflight,
-    record_capacity_refresh_joiner, record_capacity_refresh_result, record_capacity_update_completed,
-    record_capacity_update_failed, record_capacity_write_operation,
+    record_capacity_current_bytes, record_capacity_degraded_reading, record_capacity_dirty_disk_count,
+    record_capacity_refresh_inflight, record_capacity_refresh_joiner, record_capacity_refresh_result,
+    record_capacity_update_completed, record_capacity_update_failed, record_capacity_write_operation,
 };
 use rustfs_utils::{get_env_bool, get_env_u64, get_env_usize};
 use std::collections::{HashMap, HashSet};
@@ -323,6 +323,9 @@ pub struct CachedCapacity {
     pub file_count: usize,
     /// Whether it's an estimated value
     pub is_estimated: bool,
+    /// Whether the value comes from a refresh that had partial disk failures
+    /// (some disks kept their last-known values or were dropped entirely).
+    pub degraded: bool,
     /// Data source
     pub source: DataSource,
 }
@@ -336,6 +339,10 @@ pub struct CapacityUpdate {
     pub file_count: usize,
     /// Whether the value is estimated instead of exact.
     pub is_estimated: bool,
+    /// Whether the refresh behind this update had partial disk failures.
+    /// `is_estimated` only reflects sampling; this flag is the only carrier of
+    /// the "some disks failed to scan" fact (backlog#1014).
+    pub degraded: bool,
     /// Per-disk breakdown captured from a successful refresh.
     pub per_disk: Vec<DiskCapacityUpdate>,
     /// Expected disk count for a complete disk cache.
@@ -353,6 +360,7 @@ impl CapacityUpdate {
             total_used,
             file_count,
             is_estimated: false,
+            degraded: false,
             per_disk: Vec::new(),
             expected_disk_count: None,
             replaces_disk_cache: false,
@@ -366,6 +374,7 @@ impl CapacityUpdate {
             total_used,
             file_count,
             is_estimated: true,
+            degraded: false,
             per_disk: Vec::new(),
             expected_disk_count: None,
             replaces_disk_cache: false,
@@ -379,6 +388,7 @@ impl CapacityUpdate {
             total_used,
             file_count: 0,
             is_estimated: true,
+            degraded: false,
             per_disk: Vec::new(),
             expected_disk_count: None,
             replaces_disk_cache: false,
@@ -671,11 +681,14 @@ impl HybridCapacityManager {
     pub async fn update_capacity(&self, mut update: CapacityUpdate, source: DataSource) -> CapacityUpdate {
         let start = Instant::now();
 
-        if !update.per_disk.is_empty() {
+        if !update.per_disk.is_empty() || update.degraded {
             let mut disk_cache = self.disk_cache.write().await;
             let mut disk_cache_complete = self.disk_cache_complete.write().await;
 
-            let recompute = if update.replaces_disk_cache && update.expected_disk_count == Some(update.per_disk.len()) {
+            let recompute = if !update.per_disk.is_empty()
+                && update.replaces_disk_cache
+                && update.expected_disk_count == Some(update.per_disk.len())
+            {
                 disk_cache.clear();
                 for entry in &update.per_disk {
                     disk_cache.insert(
@@ -690,6 +703,11 @@ impl HybridCapacityManager {
                 *disk_cache_complete = true;
                 true
             } else if *disk_cache_complete {
+                // Merging over a complete cache also covers a degraded
+                // (partial-failure) full refresh: successfully scanned disks
+                // are refreshed while failed disks keep their last-known
+                // values, so the published total does not dip to the
+                // surviving-subset sum and bounce back on the next refresh.
                 for entry in &update.per_disk {
                     disk_cache.insert(
                         entry.disk.clone(),
@@ -722,6 +740,7 @@ impl HybridCapacityManager {
             last_update: Instant::now(),
             file_count: update.file_count,
             is_estimated: update.is_estimated,
+            degraded: update.degraded,
             source,
         });
 
@@ -741,12 +760,16 @@ impl HybridCapacityManager {
             total_used,
             file_count = update.file_count,
             estimated = update.is_estimated,
+            degraded = update.degraded,
             source = source.as_metric_label(),
             elapsed_ms = start.elapsed().as_millis() as u64,
             "capacity refresh cache updated"
         );
         record_capacity_current_bytes(total_used);
         record_capacity_update_completed(source.as_metric_label(), start.elapsed(), total_used, update.is_estimated);
+        if update.degraded {
+            record_capacity_degraded_reading(source.as_metric_label());
+        }
         update
     }
 
@@ -1675,6 +1698,7 @@ mod tests {
                     total_used: 300,
                     file_count: 3,
                     is_estimated: false,
+                    degraded: false,
                     per_disk: vec![
                         DiskCapacityUpdate {
                             disk: CapacityScopeDisk {
@@ -1709,6 +1733,7 @@ mod tests {
                     total_used: 150,
                     file_count: 1,
                     is_estimated: true,
+                    degraded: false,
                     per_disk: vec![DiskCapacityUpdate {
                         disk: CapacityScopeDisk {
                             endpoint: "node-a".to_string(),
@@ -1739,6 +1764,138 @@ mod tests {
         assert!(cached.is_estimated);
     }
 
+    fn disk_entry(endpoint: &str, drive_path: &str, used_bytes: u64, file_count: usize) -> DiskCapacityUpdate {
+        DiskCapacityUpdate {
+            disk: CapacityScopeDisk {
+                endpoint: endpoint.to_string(),
+                drive_path: drive_path.to_string(),
+            },
+            used_bytes,
+            file_count,
+            is_estimated: false,
+        }
+    }
+
+    fn full_two_disk_update() -> CapacityUpdate {
+        CapacityUpdate {
+            total_used: 200,
+            file_count: 2,
+            is_estimated: false,
+            degraded: false,
+            per_disk: vec![
+                disk_entry("node-a", "/tmp/disk-a", 100, 1),
+                disk_entry("node-b", "/tmp/disk-b", 100, 1),
+            ],
+            expected_disk_count: Some(2),
+            replaces_disk_cache: true,
+            clear_dirty_disks: Vec::new(),
+        }
+    }
+
+    #[tokio::test]
+    #[serial]
+    async fn test_update_capacity_degraded_full_refresh_merges_cache_and_does_not_oscillate() {
+        let manager = create_isolated_manager(HybridStrategyConfig::default());
+
+        // Round 1: healthy full refresh seeds a complete cache (A=100, B=100).
+        manager.update_capacity(full_two_disk_update(), DataSource::RealTime).await;
+
+        // Round 2: disk B fails mid-scan; the degraded update carries only the
+        // surviving subset's totals and per-disk entries.
+        let degraded = manager
+            .update_capacity(
+                CapacityUpdate {
+                    total_used: 100,
+                    file_count: 1,
+                    is_estimated: false,
+                    degraded: true,
+                    per_disk: vec![disk_entry("node-a", "/tmp/disk-a", 100, 1)],
+                    expected_disk_count: None,
+                    replaces_disk_cache: false,
+                    clear_dirty_disks: Vec::new(),
+                },
+                DataSource::Scheduled,
+            )
+            .await;
+
+        // Disk B keeps its last-known 100 bytes: the published total must not
+        // dip to the surviving-subset sum.
+        assert_eq!(degraded.total_used, 200);
+        assert!(degraded.degraded);
+        let cached = manager.get_capacity().await.unwrap();
+        assert_eq!(cached.total_used, 200);
+        assert!(cached.degraded);
+
+        // Round 3: disk B recovers; the healthy full refresh clears the flag
+        // and the reported total never oscillated (200 → 200 → 200).
+        let recovered = manager.update_capacity(full_two_disk_update(), DataSource::Scheduled).await;
+        assert_eq!(recovered.total_used, 200);
+        assert!(!recovered.degraded);
+        let cached = manager.get_capacity().await.unwrap();
+        assert_eq!(cached.total_used, 200);
+        assert!(!cached.degraded);
+    }
+
+    #[tokio::test]
+    #[serial]
+    async fn test_update_capacity_degraded_with_empty_per_disk_serves_merged_cache() {
+        let manager = create_isolated_manager(HybridStrategyConfig::default());
+        manager.update_capacity(full_two_disk_update(), DataSource::RealTime).await;
+
+        // Every surviving disk had intra-disk errors, so no per-disk entry is
+        // trustworthy; the complete cache must still back the published total.
+        let degraded = manager
+            .update_capacity(
+                CapacityUpdate {
+                    total_used: 40,
+                    file_count: 1,
+                    is_estimated: false,
+                    degraded: true,
+                    per_disk: Vec::new(),
+                    expected_disk_count: None,
+                    replaces_disk_cache: false,
+                    clear_dirty_disks: Vec::new(),
+                },
+                DataSource::Scheduled,
+            )
+            .await;
+
+        assert_eq!(degraded.total_used, 200);
+        assert!(degraded.degraded);
+    }
+
+    #[tokio::test]
+    #[serial]
+    async fn test_update_capacity_degraded_without_complete_cache_keeps_partial_sum() {
+        let manager = create_isolated_manager(HybridStrategyConfig::default());
+
+        // No complete cache exists: nothing to merge, the partial sum is the
+        // best available value, but it must be visibly marked degraded and the
+        // partial per-disk data must not mark the cache complete (#805).
+        let degraded = manager
+            .update_capacity(
+                CapacityUpdate {
+                    total_used: 100,
+                    file_count: 1,
+                    is_estimated: false,
+                    degraded: true,
+                    per_disk: vec![disk_entry("node-a", "/tmp/disk-a", 100, 1)],
+                    expected_disk_count: None,
+                    replaces_disk_cache: false,
+                    clear_dirty_disks: Vec::new(),
+                },
+                DataSource::Scheduled,
+            )
+            .await;
+
+        assert_eq!(degraded.total_used, 100);
+        assert!(degraded.degraded);
+        let cached = manager.get_capacity().await.unwrap();
+        assert_eq!(cached.total_used, 100);
+        assert!(cached.degraded);
+        assert!(!manager.can_refresh_dirty_subset().await);
+    }
+
     #[tokio::test]
     #[serial]
     async fn test_refresh_or_join_returns_cluster_total_for_dirty_subset() {
@@ -1751,6 +1908,7 @@ mod tests {
                     total_used: 300,
                     file_count: 3,
                     is_estimated: false,
+                    degraded: false,
                     per_disk: vec![
                         DiskCapacityUpdate {
                             disk: CapacityScopeDisk {
@@ -1784,6 +1942,7 @@ mod tests {
             total_used: 150,
             file_count: 1,
             is_estimated: true,
+            degraded: false,
             per_disk: vec![DiskCapacityUpdate {
                 disk: CapacityScopeDisk {
                     endpoint: "node-a".to_string(),
diff --git a/crates/object-capacity/src/scan.rs b/crates/object-capacity/src/scan.rs
index 0e4dd7146..75ad85f11 100644
--- a/crates/object-capacity/src/scan.rs
+++ b/crates/object-capacity/src/scan.rs
@@ -95,6 +95,26 @@ impl CapacityScanReport {
             update.expected_disk_count = Some(expected_disk_count);
             update.replaces_disk_cache = replaces_disk_cache;
             update.clear_dirty_disks = update.per_disk.iter().map(|entry| entry.disk.clone()).collect();
+        } else if self.summary.had_partial_errors {
+            // Partial failure: mark the reading degraded and surface only the
+            // disks whose own scan fully succeeded, so the manager can merge
+            // them over a complete disk cache while failed disks keep their
+            // last-known values. A disk with intra-disk errors under-counts,
+            // so its stale cache entry is closer to the truth than its scan.
+            // The cache is never replaced from a degraded refresh.
+            update.degraded = true;
+            update.per_disk = self
+                .per_disk
+                .into_iter()
+                .filter(|entry| !entry.scan.had_partial_errors)
+                .map(|entry| DiskCapacityUpdate {
+                    disk: entry.disk,
+                    used_bytes: entry.scan.used_bytes,
+                    file_count: entry.scan.file_count,
+                    is_estimated: entry.scan.is_estimated,
+                })
+                .collect();
+            update.clear_dirty_disks = update.per_disk.iter().map(|entry| entry.disk.clone()).collect();
         }
 
         update
@@ -1122,6 +1142,88 @@ mod tests {
         assert!(result.had_partial_errors);
     }
 
+    #[tokio::test]
+    async fn test_partial_scan_report_produces_degraded_update() {
+        use std::fs::File;
+        use std::io::Write;
+        use tempfile::TempDir;
+
+        let temp_dir = TempDir::new().unwrap();
+        let mut file = File::create(temp_dir.path().join("test.txt")).unwrap();
+        file.write_all(b"Hello, World!").unwrap();
+        drop(file);
+
+        let good_disk = CapacityDiskRef {
+            endpoint: "disk-1".to_string(),
+            drive_path: temp_dir.path().to_string_lossy().into_owned(),
+        };
+        let disks = vec![
+            good_disk.clone(),
+            CapacityDiskRef {
+                endpoint: "disk-2".to_string(),
+                drive_path: "/nonexistent/path".to_string(),
+            },
+        ];
+
+        let report = calculate_data_dir_used_capacity_report(&disks).await.unwrap();
+        let update = report.into_capacity_update(disks.len(), true);
+
+        // A partial full refresh is degraded and must never replace the disk
+        // cache; only the surviving disk is surfaced for cache merging.
+        assert!(update.degraded);
+        assert!(!update.replaces_disk_cache);
+        assert_eq!(update.expected_disk_count, None);
+        assert_eq!(update.per_disk.len(), 1);
+        assert_eq!(update.per_disk[0].disk, disk_scope_key(&good_disk));
+        assert_eq!(update.clear_dirty_disks, vec![disk_scope_key(&good_disk)]);
+    }
+
+    #[test]
+    fn test_into_capacity_update_partial_failure_filters_intra_disk_errors() {
+        let clean = DiskCapacityScanResult {
+            disk: CapacityScopeDisk {
+                endpoint: "node-a".to_string(),
+                drive_path: "/tmp/disk-a".to_string(),
+            },
+            scan: CapacityScanResult {
+                used_bytes: 100,
+                file_count: 1,
+                ..Default::default()
+            },
+        };
+        let partial = DiskCapacityScanResult {
+            disk: CapacityScopeDisk {
+                endpoint: "node-b".to_string(),
+                drive_path: "/tmp/disk-b".to_string(),
+            },
+            scan: CapacityScanResult {
+                used_bytes: 40,
+                file_count: 1,
+                had_partial_errors: true,
+                ..Default::default()
+            },
+        };
+        let report = CapacityScanReport {
+            summary: CapacityScanResult {
+                used_bytes: 140,
+                file_count: 2,
+                had_partial_errors: true,
+                ..Default::default()
+            },
+            per_disk: vec![clean.clone(), partial],
+        };
+
+        let update = report.into_capacity_update(3, true);
+
+        // A disk whose own scan had intra-disk errors under-counts, so it must
+        // not overwrite its last-known cached value.
+        assert!(update.degraded);
+        assert_eq!(update.per_disk.len(), 1);
+        assert_eq!(update.per_disk[0].disk, clean.disk);
+        assert_eq!(update.per_disk[0].used_bytes, 100);
+        assert!(!update.replaces_disk_cache);
+    }
+
     #[tokio::test]
     async fn test_select_capacity_refresh_disks_returns_full_when_disk_cache_incomplete() {
         let manager = create_isolated_manager(HybridStrategyConfig::default());
@@ -1159,6 +1261,7 @@ mod tests {
                     total_used: 300,
                     file_count: 3,
                     is_estimated: false,
+                    degraded: false,
                     per_disk: vec![
                         DiskCapacityUpdate {
                             disk: CapacityScopeDisk {
diff --git a/rustfs/src/capacity/service.rs b/rustfs/src/capacity/service.rs
index 16eda0cbe..f23c9bb96 100644
--- a/rustfs/src/capacity/service.rs
+++ b/rustfs/src/capacity/service.rs
@@ -127,8 +127,8 @@ pub async fn resolve_admin_used_capacity(disks: &[rustfs_madmin::Disk], fallback
         if cache_age < fast_update_threshold {
             record_capacity_cache_served("fresh");
             debug!(
-                "Using cached capacity: {} bytes (age: {:?}, source: {:?}, files={}, estimated={})",
-                cached.total_used, cache_age, cached.source, cached.file_count, cached.is_estimated
+                "Using cached capacity: {} bytes (age: {:?}, source: {:?}, files={}, estimated={}, degraded={})",
+                cached.total_used, cache_age, cached.source, cached.file_count, cached.is_estimated, cached.degraded
             );
             return cached.total_used;
         }
@@ -157,6 +157,7 @@ pub async fn resolve_admin_used_capacity(disks: &[rustfs_madmin::Disk], fallback
                         duration_ms = elapsed.as_millis() as u64,
                         file_count = update.file_count,
                         is_estimated = update.is_estimated,
+                        degraded = update.degraded,
                         "Capacity refresh completed"
                     );
                     update.total_used
@@ -188,6 +189,7 @@ pub async fn resolve_admin_used_capacity(disks: &[rustfs_madmin::Disk], fallback
             source = ?cached.source,
             file_count = cached.file_count,
             is_estimated = cached.is_estimated,
+            degraded = cached.degraded,
             needs_update,
             blocking = should_block,
             "Served cached capacity"
@@ -233,6 +235,7 @@ pub async fn resolve_admin_used_capacity(disks: &[rustfs_madmin::Disk], fallback
                 duration_ms = elapsed.as_millis() as u64,
                 file_count = update.file_count,
                 is_estimated = update.is_estimated,
+                degraded = update.degraded,
                 "Capacity refresh completed"
             );
             update.total_used