It's not totally clear based on Amazon's provided documentation. Intuitively, it feels like it'd cost twice as much as a normal RDS instance for a two-zone deployment; does anyone here have experience with this, and could confirm or disconfirm that?
Amazon's RDS pricing page has two sections. One for Single-AZ Deployment and one for Multi-AZ Deployment.
Yes, Multi-AZ is about twice the price of Single-AZ. For example I see:
- db.t2.micro single - $0.017/hour
- db.t2.micro multi - $0.034/hour
To estimate the RDS cost I recommend the AWS Simple Monthly Calculator.
db.m4.large PostgreSQL instance I get the following:
- Single-AZ - $140.13/month - no High Availability
- Multi-AZ - $280.25/month
This means: Single-AZ cost = ½ Multi-AZ cost
Below two screenshots:
PS: no data transfer costs, no additional backup costs included
Old thread but it's searchable...
If you run multiple instances in multiple AZs, of course you pay for each instance. There is some additional data replication costs but the BIG miss here is that you have two instances to handle your load. If this follows the pattern of many more DB reads than writes that is common in apps, I would have the consumers deployed to 2 or 3 AZs with writes going to the "main" instance distributing reads across both instances.
Having two instances and and only using one is not the best imlementation