@item cache-clean-interval
Clean unused entries in the L2 and refcount caches. The interval is in seconds.
-The default value is 0 and it disables this feature.
+The default value is 600 on supporting platforms, and 0 on other platforms.
+Setting it to 0 disables this feature.
@item pass-discard-request
Whether discard requests to the qcow2 device should be forwarded to the data