Merge pull request #316 from danhermann/master

added tips about performance schema, global variables, and Aurora multi-AZ considerations

README.md

@@ -1126,14 +1126,16 @@ RDS MySQL and MariaDB
 ### RDS MySQL and MariaDB Tips
 
 -	MySQL RDS allows access to [binary logs](http://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/USER_LogAccess.Concepts.MySQL.html#USER_LogAccess.MySQL.BinaryFormat).
--	Multi-AZ instances of MySQL transparently replicate data across AZs using DRBD. Automated backups of multi-AZ instances [run off the backup instance](https://www.percona.com/live/mysql-conference-2014/sessions/rds-mysql-tips-patterns-and-common-pitfalls) to reduce latency spikes on the primary.
--	🔸**MySQL vs MariaDB vs Aurora:** If you prefer a MySQL-style database but are starting something new, you probably should consider Aurora and MariaDB as well. **Aurora** has increased availability and is the next-generation solution. That said, Aurora [may not be](http://blog.takipi.com/benchmarking-aurora-vs-mysql-is-amazons-new-db-really-5x-faster/) as fast relative to MySQL as is sometimes reported, and is more complex to administer. **MariaDB**, the modern [community fork](https://en.wikipedia.org/wiki/MariaDB) of MySQL, [likely now has the edge over MySQL](http://cloudacademy.com/blog/mariadb-vs-mysql-aws-rds/) for many purposes and is supported by RDS.
+-	Multi-AZ instances of MySQL transparently replicate data across AZs using DRBD. Automated backups of multi-AZ instances [run off the backup instance](https://www.percona.com/live/mysql-conference-2014/sessions/rds-mysql-tips-patterns-and-common-pitfalls) to reduce latency spikes on the primary.  
+-	🔸**Performance Schema:** While [Performance Schema](http://dev.mysql.com/doc/refman/en/performance-schema.html) is enabled by default in MySQL 5.6.6 and later, it is disabled by default in all versions of RDS. If you wish to enable Performance Schema, a reboot of the RDS instance will be required. 
+-	🔸**MySQL vs MariaDB vs Aurora:** If you prefer a MySQL-style database but are starting something new, you probably should consider Aurora and MariaDB as well. **Aurora** has increased availability and is the next-generation solution. That said, Aurora [may not be](http://blog.takipi.com/benchmarking-aurora-vs-mysql-is-amazons-new-db-really-5x-faster/) that much faster than MySQL for certain workloads. **MariaDB**, the modern [community fork](https://en.wikipedia.org/wiki/MariaDB) of MySQL, [likely now has the edge over MySQL](http://cloudacademy.com/blog/mariadb-vs-mysql-aws-rds/) for many purposes and is supported by RDS.
 
 ### RDS MySQL and MariaDB Gotchas and Limitations
 
 -	🔸**No SUPER privileges.** RDS provides some [stored procedures](http://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/Appendix.MySQL.SQLRef.html) to perform some tasks that require SUPER privileges such as starting or stopping replication.
 -	🔸You can replicate to non-RDS instances of MySQL, but [replication to these instances will break during AZ failovers](https://www.percona.com/live/mysql-conference-2014/sessions/rds-mysql-tips-patterns-and-common-pitfalls).
 -	🔸There is no ability to manually CHANGE MASTER on replicas, so they must all be rebuilt after a failover of the master.
+-	🔸Most global options are exposed only via [DB parameter groups](https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/USER_WorkingWithParamGroups.html). Some variables that were introduced in later MySQL dot releases such as [avoid_temporal_upgrade](https://dev.mysql.com/doc/refman/5.6/en/server-system-variables.html#sysvar_avoid_temporal_upgrade) in MySQL 5.6.24 are not made available in RDS's 5.6.x parameter group and making use of them requires an upgrade to MySQL 5.7.x. 
 
 RDS Aurora
 -----------
@@ -1154,6 +1156,7 @@ RDS Aurora
 -	Because Aurora is based on MySQL 5.6.10, avoiding any MySQL features from 5.7 or later will ease the transition from a MySQL-compatible database into Aurora.
 -	The easiest migration path to Aurora is restoring a database snapshot from MySQL 5.6. The next easiest method is restoring a dump from a MySQL-compatible database such as MariaDB. For [low-downtime migrations](http://cantrill.io/howto/aws/2016/06/06/migrating-from-mysql-to-aurora-with-almost-no-downtime.html) from other MySQL-compatible databases, you can set up an Aurora instance as a replica of your existing database. If none of those methods are options, Amazon offers a fee-based data migration service.
 -	You can replicate [from an Aurora cluster to MySQL or to another Aurora cluster](http://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/Aurora.Overview.Replication.MySQLReplication.html). This requires binary logging to be enabled and is not as performant as native Aurora replication.
+-	Because Aurora read replicas are the [equivalent of a multi-AZ backup](http://stackoverflow.com/a/32428651/129052) and they can be configured as zero-data-loss failover targets, there are fewer scenarios in which the creation of a multi-AZ Aurora instance is required.
 
 ### RDS Aurora Gotchas and Limitations