updates

Pro-2.0-Upgrade.md

@@ -5,16 +5,20 @@ how features are activated. To upgrade cleanly:
 
 ## Batches
 
+The batch data model was overhauled.  Batch data should take
+significantly less space in Redis now.  A simple benchmark shows 25%
+savings.
+
 * Batch 2.x BIDs are 14 character URL-safe Base64-encoded strings, e.g.
-  "vTF1-9QvLPnREQ".
-  Batch 1.x BIDs were 16 character hex-encoded strings, e.g. "4a3fc67d30370edf".
-* In 1.x, batch data expired after 72 hours.  In 2.x, all data in Redis
-  for a batch is removed once the batch has run any success callbacks.
+  "vTF1-9QvLPnREQ".  Batch 1.x BIDs were 16 character hex-encoded
+  strings, e.g. "4a3fc67d30370edf".
+* In 1.x, batch data was not removed until it naturally expired in Redis.
+  In 2.x, all data for a batch is removed from Redis once the batch has
+  run any success callbacks.
 * Because of the former point, batch expiry is no longer a concern.
   Batch expiry is hardcoded to 30 days and is no longer user-tunable.
-* Sidekiq::Batch#notify was removed.  This API was a very thin layer
-  on top of the more flexible `Sidekiq::Batch#on` API that everyone
-  should be using.
+* Failed batch jobs no longer automatically store any associated
+  backtrace in Redis unless the job's `backtrace` option is set.
 * You must require `sidekiq/notifications` if you want to use the
   pre-defined notification schemes.