![](https://i.imgur.com/7UFUiDY.png)
- Amazon Web Services
- Custom Backend! - Not AWS Services
- EC2 - general server/vm
- S3 - store snapshots
![](https://i.imgur.com/OxFuxrX.png)
- persist to EBS
- Availability Zones
![](https://i.imgur.com/LjBawGD.png)
![](https://i.imgur.com/uGcC9Pu.png)
![](https://i.imgur.com/s0Wlvyl.png)
- replicas with quorum
- just log entries
- only need 4 out of 6!
- doing this instead of having to replicate the page table (like RDS) 35x performance!
![](https://i.imgur.com/VEK0C7U.png)
- goals of survival of failure of datacenter (AZ)
- transient slow replicas (?)
![](https://i.imgur.com/bwml8lR.png)
- quorum replication
- n replicas
- read and write quorum must overlap
- W and R
![](https://i.imgur.com/rZCfJ19.png)
- databases vm/servers can crash
- spin up new server log says redo these in the transactions
- many many pages
![](https://i.imgur.com/HqkjpK4.png)
- copy of A, B, etc on different servers
- replacement, pick 100 segment services
- pick 1 replica from each
- reads more common than writes
- atomicly