diff --git a/lib/swift b/lib/swift
index f72beaf..3dcd8b6 100644
--- a/lib/swift
+++ b/lib/swift
@@ -55,7 +55,13 @@
 # swift data. Set ``SWIFT_LOOPBACK_DISK_SIZE`` to the disk size in
 # kilobytes.
 # Default is 1 gigabyte.
-SWIFT_LOOPBACK_DISK_SIZE=${SWIFT_LOOPBACK_DISK_SIZE:-1000000}
+SWIFT_LOOPBACK_DISK_SIZE_DEFAULT=1048576
+# if tempest enabled the default size is 4 Gigabyte.
+if is_service_enabled tempest; then
+    SWIFT_LOOPBACK_DISK_SIZE_DEFAULT=${SWIFT_LOOPBACK_DISK_SIZE:-4194304}
+fi
+
+SWIFT_LOOPBACK_DISK_SIZE=${SWIFT_LOOPBACK_DISK_SIZE:-$SWIFT_LOOPBACK_DISK_SIZE_DEFAULT}
 
 # Set ``SWIFT_EXTRAS_MIDDLEWARE`` to extras middlewares.
 # Default is ``staticweb, tempurl, formpost``