Jira DOC-814: RC - Clarify high-availability article (#1448)

* Quick edits to rework plan names.

* Initial draft of updates.

content/rc/databases/high-availability.md

@@ -11,25 +11,39 @@ aliases:
 
 Database replication helps ensure high availability. When replication is enabled, your dataset is duplicated to create a replica, which stays in sync with the primary dataset. Replication allows for automatic failover and greater fault tolerance. This can prevent data loss in the event of a hardware or zone failure. 
 
+## Options and plan support
+
 Redis Enterprise Cloud supports three levels of replication:
 
 - _No replication_ means that you will have a single copy of your database.
 - _Single-zone replication_ means that your database will have a primary and a replica located in the same zone of a cloud region. 
 - _Multi-zone replication_ means that the primary and its replicas are stored in different zones of a cloud region. This means that your database can remain online even if an entire zone becomes unavailable.
 
-Your replication options depend on which subscription plan you're using:
+Your replication options depend on your [subscription plan]({{<relref "/rc/subscriptions/_index.md">}}):
 
 - _Free_ plans do not support replication.
 - _Fixed_ plans let you choose between no replication, single-zone replication, or multi-zone replication when creating a subscription.  
+- _Flexible_ and _Annual_ plans allow multi-zone or single-zone subscriptions by default.  You can also disable replication.
+
+## Performance impact 
+
+Replication can affect performance as traffic increases to synchronize all copies. 
+
+Database storage costs also increase:
+
+- For Fixed plans, single-zone and multi-zone replication effectively doubles storage costs
+
+- For Flexible and Annual plans, replication requires additional shards
+
+## Zone setting maintenance
 
-Zone settings cannot be changed once a subscription has been created.  This means you can't convert a multi-zone subscription to a single zone (or vice-versa).
+Zone settings can only be defined when a subscription is created.  You cannot change these settings once the subscription becomes active.
 
-If this becomes necessary, create a new subscription with the preferred settings and then migrate data from the original subscription.```
-- _Flexible_ plans allow multi-zone or single-zone subscriptions by default.  Each type allows replication to be disabled entirely.  
+This means you can't convert a multi-zone subscription to a single zone (or vice-versa).  
 
-   Once the subscription is created, though, you cannot switch zone settings. 
+To use different zone settings, create a new subscription with the preferred settings and then migrate data from the original subscription.
 
-To learn more about Redis Enterprise Cloud subscriptions, see [Manage subscriptions]({{<relref "/rc/subscriptions/_index.md">}}).
+## More info
 
 To learn more about high availability and replication, see:
 - [Highly Available Redis](https://redislabs.com/redis-enterprise/technology/highly-available-redis/)