copy docs

docs/markdown/_toc.md

@@ -14,6 +14,7 @@
 > > [Overview](/location/options)
 > > [Excluding Files](/location/exclude)
 > > [Forget Policy](/location/forget)
+> > [Copy](/location/copy)
 >
 > [Cron](/location/cron)
 > [Docker Volumes](/location/docker)

docs/markdown/location/copy.md

@@ -0,0 +1,31 @@
+# Copy
+
+Instead of specifying multiple `to` backends for a given `location` you can also use the `copy` option. Instead of recalculating the backup multiple times, you can copy the freshly copied snapshot from one backend to the other, avoiding recomputation.
+
+###### Example
+
+```yaml | .autorestic.yml
+locations:
+  my-location:
+    from: /data
+    to:
+      - a #Fast
+      - b #Fast
+      - c #Slow
+```
+
+Becomes
+
+```yaml | .autorestic.yml
+locations:
+  my-location:
+    from: /data
+    to:
+      - a
+      - b
+    copy:
+      a:
+        - c
+```
+
+Instead of backing up to each backend separately, you can choose that the snapshot created to `a` will be copied over to `c`, avoiding heavy computation on `c`.