AlwaysOn Availability Groups Way Too Deep Joey D’Antoni SQL Saturday #164 Cleveland 18 August 2012
About Me Principal Architect SQL Server, Comcast Cable @jdanton Joedantoni.wordpress.com (Slides will be here and on SQL Sat site) firstname.lastname@example.org
Agenda Overview of AlwaysOn Extended Events Briefly What Happens When? Turn on AlwaysOn We Build an Availability Group We add data to a Primary DB We backup the transaction log on the secondary We query the secondary DB
Warning You are going to see a few things that aren’t fully documented We aren’t touching anything—just looking to see what’s going on I’m telling you what I think is happening, I’m still trying to get answers on some of it
Moving Data Database Mirroring used a single thread per database to move data Always On is different—it uses a request pool that is shared between all AlwaysOn Databases On the primary messages the active log scanner is the log pole. When a secondary is ready to receive log blocks a message is sent to the primary to start the log scanning. This message is handled by a worker in the HadrThreadPool.