View stunning SlideShares in full-screen with the new iOS app!Introducing SlideShare for AndroidExplore all your favorite topics in the SlideShare appGet the SlideShare app to Save for Later — even offline
View stunning SlideShares in full-screen with the new Android app!View stunning SlideShares in full-screen with the new iOS app!
Why do we need Replication?• Failover• Backups• Secondary Batch Jobs• High Availability 15
Outages• Planned – Hardware upgrade – OS or file-system tuning – Software upgrade – Relocation of data to new file-system / storage• Un-planed – Human Error – Hardware Failure – Data Center / Region Outage – Application Corruption 16
Replica Sets• Data Protection – Multiple copies of data – Data spread across data centers, AZ’s etc• High Availability – Automated Failover – Automated Recovery 17
Consistency• Eventual Consistency – Allow updates when a system as been partitioned – Resolve conflicts later – Ex: Cassandra, CouchDB• Immediate Consistency – Single Master – Avoids conflicts – Example: MongoDB 32
Durability• For how long is my data available?• When do I know my data is safe?!• Where is it safe?• MongoDB style: – Fire and Forget – Get Last Error – Journal Sync – Replica Safe 33