release-notes/6.0: Add ctime feature changes in release notes

Change-Id: I3a305b9eb292a450c83de5628ceeadcb0a44afc7
updates: bz#1672818
Signed-off-by: Kotresh HR <khiremat@redhat.com>
Signed-off-by: ShyamsundarR <srangana@redhat.com>

doc/release-notes/6.0.md

@@ -156,6 +156,31 @@ Samba unless either of 'user.cifs' or 'user.smb' volume set options are enabled
 on the volume. The existing GlusterFS volume share sections in smb.conf will
 remain unchanged.
 
+#### 7. ctime feature is enabled by default
+
+The ctime feature which maintains (c/m) time consistency across replica and
+disperse subvolumes is enabled by default.
+
+Also, with this release, a single option is provided to enable/disable ctime
+feature,
+
+```
+#gluster vol set <volname> ctime <on/off>
+```
+
+**NOTE:** The time information used is from clients, hence it's required that
+clients are synced with respect to their times, using NTP or other such means.
+
+**Limitations:**
+- Mounting gluster volume with time attribute options (noatime, realatime...)
+  is not supported with this feature
+- This feature does not guarantee consistent time for directories if the hashed
+  sub-volume for the directory is down
+- Directory listing is not supported with this feature, and may report
+  inconsistent time information
+- Older files created before upgrade, would witness update of ctime upon
+  accessing after upgrade [BUG:1593542](https://bugzilla.redhat.com/show_bug.cgi?id=1593542)
+
 ### Developer
 
 #### 1. Gluster code can be compiled and executed using [TSAN](https://clang.llvm.org/docs/ThreadSanitizer.html)