4 ms·

So if the hardware running the database is suddenly destroyed they try to start another instance really fast? That seems inferior to having multiple sync repli

by devit 6y ago

So if the hardware running the database is suddenly destroyed they try to start another instance really fast? That seems inferior to having multiple sync replicas ready to take over without having to start a process and replay the WAL. Also, such an HA block store seems very easy to replicate ( I'd guess there would be something open source already), not much of a competitive advantage.

redis_mlc 6y ago
- using block-level replication allows them to support multiple databases in a common way - block-level replication can be more reliable in the long run operationally than some types of database replication, especially MySQL back in the day - block-level replication has more scalable support staff available than hiring DBAs to fix database replication problems - programming for all the edge cases is something that is a competitive advantage - no licensing required for it - you can probably guess which Open Source project it's based on Source: DBA, worked there.
- hashhar 6y ago
  Just gonna put this here for people who might be wondering. Not too many block-level replication implementations exist. https://www.linbit.com/drbd/ https://www.linbit.com/drbd/ NB: It is Free software, don't be alarmed by the domain name.
- bratao 6y ago
  Linstor can do that. I use in Kubernetes and it is incredible!
aeyes 6y ago
There are two types of failover in RDS: - Single instance, if the instance dies they start a new one and mount the same storage. This can take some time, in general under 5min but I have seen it take 45min, especially for the large instance types. - Multi A-Z, they run a hot standby with replicated and physically separated storage. Failover takes about a minute. The replication happens at storage level, every write has to be acknowledged by both availability zones. I'm not sure if Postgres is always running or if it gets started when failing over. I guess you could replicate this using drbd.

by devit 6y ago

redis_mlc 6y ago

- using block-level replication allows them to support multiple databases in a common way - block-level replication can be more reliable in the long run operationally than some types of database replication, especially MySQL back in the day - block-level replication has more scalable support staff available than hiring DBAs to fix database replication problems - programming for all the edge cases is something that is a competitive advantage - no licensing required for it - you can probably guess which Open Source project it's based on Source: DBA, worked there.

hashhar 6y ago
Just gonna put this here for people who might be wondering. Not too many block-level replication implementations exist. https://www.linbit.com/drbd/ https://www.linbit.com/drbd/ NB: It is Free software, don't be alarmed by the domain name.
bratao 6y ago
Linstor can do that. I use in Kubernetes and it is incredible!

aeyes 6y ago

There are two types of failover in RDS: - Single instance, if the instance dies they start a new one and mount the same storage. This can take some time, in general under 5min but I have seen it take 45min, especially for the large instance types. - Multi A-Z, they run a hot standby with replicated and physically separated storage. Failover takes about a minute. The replication happens at storage level, every write has to be acknowledged by both availability zones. I'm not sure if Postgres is always running or if it gets started when failing over. I guess you could replicate this using drbd.