Document save_storage and 'SAVE_STORAGE_TIMEOUT'

doc/backend_vars.asciidoc

@@ -200,6 +200,7 @@ WORKER_CLASS;string;undef;qemu system types
 WORKER_HOSTNAME;string;undef;Worker hostname
 QEMU_VIDEO_DEVICE;string;virtio-gpu-pci on ARM, VGA otherwise;Video device to use with VM (using -device, not -vga). Can have options appended e.g. "virtio-gpu-gl,edid=on", but it is better to set QEMU_VIDEO_DEVICE_OPTIONS. See qemu docs and https://www.kraxel.org/blog/2019/09/display-devices-in-qemu/ for valid choices
 QEMU_VIDEO_DEVICE_OPTIONS;string;none;Additional options for QEMU_VIDEO_DEVICE (comma-separated). Will be appended after automatically-generated resolution setting options on devices that support EDID
+SAVE_STORAGE_TIMEOUT;integer;900;Specifies timeout for saving one storage drive in `save_storage` test API function.
 |====================
 
 .SVIRT backend

doc/memorydumps.asciidoc

@@ -8,10 +8,10 @@ IMPORTANT: Currently only the QEMU backend is supported.
 
 == How to use
 
-Two methods are available to the test writer, `freeze_vm` and `save_memory_dump`
+Three methods are available to the test writer, `freeze_vm`, `save_memory_dump` and `save_storage`
 
 The feature is enabled by calling the aforementioned methods, using
-a https://github.com/os-autoinst/openQA/blob/master/docs/WritingTests.asciidoc#how-to-write-tests[post_fail_hook] and setting the test's flags as fatal. The `save_memory_dump` method can be however
+a https://github.com/os-autoinst/openQA/blob/master/docs/WritingTests.asciidoc#how-to-write-tests[post_fail_hook] and setting the test's flags as fatal. The `save_memory_dump`  and `save_storage` methods can be however
 called at any point within the test.
 
 === save_memory_dump
@@ -29,6 +29,14 @@ without any risk of data changing.
 
 NOTE: Call this method to ensure memory and disk dump refer to the same machine state.
 
+
+=== save_storage
+
+If it is supported by the backend `save_storage` will save all storage devices into backup.
+This can be called from anywhere within a test. For multiple calls within a test module a filename needs to be specified. By default it uses the test module name.
+
+NOTE: This method is time-consuming and requires a lot of space.
+
 == Examples
 
 A very simple way to use this helpful feature is the following:
@@ -42,3 +50,8 @@ sub post_fail_hook ($self) {
 
 sub test_flags ($) { { fatal => 1 } }
 ----------------------------------------
+
+[source,perl]
+----------------------------------------
+    save_storage(filename => 'my-backup');
+----------------------------------------