fix(release): keep large snapshots attached and low impact

deploy/unraid/deploy-release.sh

@@ -355,14 +355,34 @@ print(
 PY
 }
 
+run_low_impact() {
+  local priority_command=()
+
+  # Backups are mandatory, but their first byte-complete copy and SHA-256
+  # verification must not starve the live Unraid services. BusyBox hosts do
+  # not always provide both tools, so use every available scheduler without
+  # weakening the backup when one is absent.
+  if command -v ionice >/dev/null 2>&1; then
+    priority_command+=(ionice -c 2 -n 7)
+  fi
+  if command -v nice >/dev/null 2>&1; then
+    priority_command+=(nice -n 10)
+  fi
+  if [ "${#priority_command[@]}" -eq 0 ]; then
+    "$@"
+    return
+  fi
+  "${priority_command[@]}" "$@"
+}
+
 select_verified_link_dest() {
   local candidate=""
   GEOINTEL_BACKUP_LINK_DEST=""
   while IFS= read -r candidate; do
     if (
       cd "$candidate" \
-        && sha256sum -c CHECKSUMS.sha256 >/dev/null \
-        && python3 "$ROOT/scripts/release_backup_snapshot.py" verify-backup --backup-dir "$candidate"
+        && run_low_impact sha256sum -c CHECKSUMS.sha256 >/dev/null \
+        && run_low_impact python3 "$ROOT/scripts/release_backup_snapshot.py" verify-backup --backup-dir "$candidate"
     ); then
       GEOINTEL_BACKUP_LINK_DEST="$candidate"
       echo "Using verified prior byte snapshot as link-dest: ${candidate}"
@@ -482,7 +502,7 @@ PY
 
   GEOINTEL_PREDEPLOY_BACKUP_DIR="${GEOINTEL_BACKUPS_PATH%/}/${release_id}"
   echo "Creating mandatory pre-deploy backup ${release_id}..."
-  if ! bash scripts/backup_release_state.sh \
+  if ! run_low_impact bash scripts/backup_release_state.sh \
       --container geointel \
       --output-root "$GEOINTEL_BACKUPS_PATH" \
       --release-id "$release_id" \
@@ -491,7 +511,7 @@ PY
       --inventory-mode sha256 \
       --rollback-image-tag "$GEOINTEL_PREDEPLOY_ROLLBACK_TAG" \
       "${backup_link_args[@]}" \
-    || ! bash scripts/verify_release_backup.sh \
+    || ! run_low_impact bash scripts/verify_release_backup.sh \
       --container geointel \
       --backup-dir "$GEOINTEL_PREDEPLOY_BACKUP_DIR"; then
     echo "Pre-deploy backup failed; restarting the unchanged current release." >&2