let user set ionice in settings

backend/app/core/utils.py

@@ -4,6 +4,54 @@ import sys
 from loguru import logger
 
 
+def _get_ionice_setting() -> str:
+    """Reads the user's preferred I/O scheduling class from settings."""
+    try:
+        from app.db.database import SessionLocal
+        from app.db import models
+
+        with SessionLocal() as db_session:
+            record = (
+                db_session.query(models.SystemSetting)
+                .filter(models.SystemSetting.key == "ionice_level")
+                .first()
+            )
+            if record and record.value in ("idle", "best-effort", "realtime"):
+                return record.value
+    except Exception:
+        pass
+    return "idle"  # Default: be the most polite
+
+
+def set_process_priority(level: str):
+    """Adjusts CPU and I/O priority of the current process.
+
+    Args:
+        level: "background" for lowest priority (ionice idle + nice 19),
+               "normal" to reset (ionice best-effort + nice 0).
+    """
+    try:
+        import psutil
+
+        p = psutil.Process(os.getpid())
+        if level == "background":
+            ionice_level = _get_ionice_setting()
+            if hasattr(p, "ionice"):
+                if ionice_level == "idle":
+                    p.ionice(psutil.IOPRIO_CLASS_IDLE)  # type: ignore[attr-defined]
+                elif ionice_level == "realtime":
+                    p.ionice(psutil.IOPRIO_CLASS_RT)  # type: ignore[attr-defined]
+                else:
+                    p.ionice(psutil.IOPRIO_CLASS_BE)  # type: ignore[attr-defined]
+            p.nice(19)
+        else:
+            if hasattr(p, "ionice"):
+                p.ionice(psutil.IOPRIO_CLASS_BE)  # type: ignore[attr-defined]
+            p.nice(0)
+    except Exception as e:
+        logger.debug(f"Could not set process priority to '{level}': {e}")
+
+
 def get_path_uuid(path: str) -> str | None:
     """Attempts to retrieve a stable hardware/filesystem UUID for a given path."""
     if not os.path.exists(path):

backend/app/services/archiver.py

@@ -307,6 +307,10 @@ class ArchiverService:
         )
         JobManager.add_job_log(job_id, f"Starting backup to {media_record.identifier}")
 
+        from app.core.utils import set_process_priority
+
+        set_process_priority("background")
+
         workload_batch = self.assemble_backup_batch(db_session, media_id)
         if not workload_batch:
             JobManager.add_job_log(job_id, "No files require backup")
@@ -744,6 +748,7 @@ class ArchiverService:
             logger.exception(f"Archival failed: {e}")
             JobManager.fail_job(job_id, str(e))
         finally:
+            set_process_priority("normal")
             # Clean up any residual staging files
             for chunk_file in os.listdir(self.staging_directory):
                 if chunk_file.startswith("backup_") and chunk_file.endswith(".tar"):

backend/app/services/scanner.py

@@ -169,23 +169,6 @@ class ScannerService:
                     return
                 time.sleep(0.1)
 
-    def _set_process_priority(self, level: str):
-        """Adjusts the CPU and I/O priority of the current process."""
-        try:
-            p = psutil.Process(os.getpid())
-            if level == "background":
-                if hasattr(p, "ionice"):
-                    p.ionice(
-                        psutil.IOPRIO_CLASS_IDLE  # ty: ignore[unresolved-attribute]
-                    )
-                p.nice(19)
-            else:
-                if hasattr(p, "ionice"):
-                    p.ionice(psutil.IOPRIO_CLASS_BE)  # ty: ignore[unresolved-attribute]
-                p.nice(0)
-        except Exception:
-            pass
-
     def compute_sha256(
         self, file_path: str, job_id: Optional[int] = None
     ) -> Optional[str]:
@@ -231,7 +214,9 @@ class ScannerService:
             JobManager.update_job(job_id, 0.0, "Starting system scan...")
             JobManager.add_job_log(job_id, "Starting system scan")
 
-        self._set_process_priority("normal")
+        from app.core.utils import set_process_priority
+
+        set_process_priority("normal")
         with self._metrics_lock:
             self.files_processed = 0
             self.files_new = 0
@@ -434,7 +419,9 @@ class ScannerService:
         with self._metrics_lock:
             self.is_hashing = True
 
-        self._set_process_priority("background")
+        from app.core.utils import set_process_priority
+
+        set_process_priority("background")
 
         try:
             with SessionLocal() as db_session:

frontend/src/routes/settings/+page.svelte

@@ -20,7 +20,8 @@
         Upload,
         Terminal,
         Globe,
-        Key
+        Key,
+        ChevronDown
     } from "lucide-svelte";
     import { Button } from "$lib/components/ui/button";
     import PageHeader from "$lib/components/ui/PageHeader.svelte";
@@ -51,6 +52,7 @@
     let scanSchedule = $state("");
     let archivalSchedule = $state("");
     let notificationUrls = $state<string[]>([]);
+    let ioniceLevel = $state("idle");
 
     // Secrets keystore
     let secretsList = $state<string[]>([]);
@@ -66,7 +68,8 @@
         globalExclusions,
         scanSchedule,
         archivalSchedule,
-        notificationUrls
+        notificationUrls,
+        ioniceLevel
     }));
 
     beforeNavigate((navigation: any) => {
@@ -155,6 +158,7 @@
                 if (data.schedule_scan) scanSchedule = data.schedule_scan;
                 if (data.schedule_archival) archivalSchedule = data.schedule_archival;
                 if (data.notification_urls) notificationUrls = JSON.parse(data.notification_urls);
+                if (data.ionice_level) ioniceLevel = data.ionice_level;
             }
 
             // Load secrets
@@ -169,7 +173,8 @@
                 globalExclusions,
                 scanSchedule,
                 archivalSchedule,
-                notificationUrls
+                notificationUrls,
+                ioniceLevel
             });
         } catch (error) {
             toast.error("Failed to load system configuration");
@@ -188,7 +193,8 @@
                 updateSettings({ body: { key: "global_exclusions", value: globalExclusions } }),
                 updateSettings({ body: { key: "schedule_scan", value: scanSchedule } }),
                 updateSettings({ body: { key: "schedule_archival", value: archivalSchedule } }),
-                updateSettings({ body: { key: "notification_urls", value: JSON.stringify(notificationUrls) } })
+                updateSettings({ body: { key: "notification_urls", value: JSON.stringify(notificationUrls) } }),
+                updateSettings({ body: { key: "ionice_level", value: ioniceLevel } })
             ]);
 
             // Snapshot saved state
@@ -199,7 +205,8 @@
                 globalExclusions,
                 scanSchedule,
                 archivalSchedule,
-                notificationUrls
+                notificationUrls,
+                ioniceLevel
             });
 
             toast.success("System configuration committed");
@@ -648,6 +655,24 @@
 
                 {:else if activeTab === 'system'}
                     <div class="animate-in slide-in-from-bottom-4 duration-500 space-y-6">
+                        <Card class="p-5 shadow-xl">
+                            <SectionHeader title="I/O scheduling" icon={Cpu} class="mb-6 px-0" />
+                            <div class="space-y-4">
+                                <div class="space-y-2">
+                                    <label class="text-xs font-medium text-text-secondary ml-1" for="ionice-level">Background job I/O priority</label>
+                                    <div class="relative">
+                                        <select id="ionice-level" bind:value={ioniceLevel} class="w-full h-10 bg-bg-primary border border-border-color rounded-xl px-4 pr-10 text-sm font-medium text-text-primary outline-none focus:ring-2 focus:ring-blue-500/20 transition-all appearance-none cursor-pointer">
+                                            <option value="idle">Idle (only use I/O when system is free)</option>
+                                            <option value="best-effort">Best-effort (normal scheduling)</option>
+                                            <option value="realtime">Real-time (highest priority, requires root)</option>
+                                        </select>
+                                        <ChevronDown size={16} class="absolute right-3 top-1/2 -translate-y-1/2 text-text-secondary pointer-events-none" />
+                                    </div>
+                                    <p class="text-[10px] text-text-secondary leading-tight opacity-60">Applies to scan and backup jobs. Idle is recommended for production systems.</p>
+                                </div>
+                            </div>
+                        </Card>
+
                         <Card class="p-5 shadow-xl">
                             <SectionHeader title="Index management" icon={Database} class="mb-6 px-0" />
                             <div class="grid grid-cols-2 gap-4">