librbd: switch to write-around cache policy by default

Signed-off-by: Jason Dillaman <dillaman@redhat.com>

diff --git a/PendingReleaseNotes b/PendingReleaseNotes
index 52f9c261ea69d01204d49d988ff47b1ee5580ea9..255ac9f0ba147abf26fbfc3b780a4b16296347c1 100644 (file)
--- a/PendingReleaseNotes
+++ b/PendingReleaseNotes
@@ -11,3 +11,12 @@
   python3.4, because EPEL7 recently switched from python3.4 to
   python3.6 as the native python3. see the `announcement <https://lists.fedoraproject.org/archives/list/epel-announce@lists.fedoraproject.org/message/EGUMKAIMPK2UD5VSHXM53BH2MBDGDWMO/>_`
   for more details on the background of this change.
+
+* librbd now uses a write-around cache policy be default,
+  replacing the previous write-back cache policy default.
+  This cache policy allows librbd to immediately complete
+  write IOs while they are still in-flight to the OSDs.
+  Subsequent flush requests will ensure all in-flight
+  write IOs are completed prior to completing. The
+  librbd cache policy can be controlled via a new
+  "rbd_cache_policy" configuration option.

diff --git a/src/common/options.cc b/src/common/options.cc
index 849aa94b135e783f5e321368516f0d1fd9717a7e..da82ba3e28c0150f54f3dbbd887140f2c8d1e672 100644 (file)
--- a/src/common/options.cc
+++ b/src/common/options.cc
@@ -6992,7 +6992,7 @@ static std::vector<Option> get_rbd_options() {
 
     Option("rbd_cache_policy", Option::TYPE_STR, Option::LEVEL_ADVANCED)
     .set_enum_allowed({"writethrough", "writeback", "writearound"})
-    .set_default("writeback")
+    .set_default("writearound")
     .set_description("cache policy for handling writes."),
 
     Option("rbd_cache_writethrough_until_flush", Option::TYPE_BOOL, Option::LEVEL_ADVANCED)