I have one Oracle SE instance that is not multi-az and does not have encryption enabled, and I have an Oracle EE instance that is multi-az and has encryption enabled. The former has the option to change the subnet group through the console (modify instance > network and security), whereas the latter does not. Both instances are in a subnet group within the default vpc, and I have a custom vpc within the same account with another subnet group in it.
What conditions determine whether or not it is possible to change the subnet group of an RDS instance? I have not been able to find any documentation on this so far.
It is the Multi AZ Deployment that is the determining factor. To test this, modify your DB instance and turn off the Multi AZ Deployment. Once it is done, go modify it again and you'll notice you now have the option to change the subnet group.
I haven't found any indication as to the reason for this behavior in the AWS documentation.
As #hackakhan mentioned, you need to have Multi AZ Deployment turned off to modify the DB subnet group of an RDS instance. Unfortunately, the RDS instance will only be migrated to one of the subnets from the new DB subnet group if the new DB subnet group resides in a different VPC. You could create a temporary VPC to migrate away the RDS instance only to migrate it back to your existing VPC and the right DB subnet group within that VPC.
The AWS Premium Support Knowledge Center has a detailed explanation of the steps involved: https://aws.amazon.com/premiumsupport/knowledge-center/change-vpc-rds-db-instance/
My understanding
RDS instances can't be migrated from one database subnet group to another if:
The destination database subnet group is in the same VPC as the current group
The instance has the multi-availability zone setting enabled
What worked for me
Creating the subnet group within my VPC that would be the eventual home of my RDS instance
Creating a temporary database subnet group in the "DEFAULT" VPC (my RDS instance has previously been a subnet group in a VPC that I had provisioned, not the default one) consisting of the three subnets that belong to the "DEFAULT" VPC—this can be done in the RDS section of the AWS Console, no need to go to the VPC section
Modifying the instance's subnet group to the newly created group (from 2.)
Modifying the instance's subnet group to its eventual home within my original VPC (from 1.)
Related
I haven't changed my vpc/subnet settings since making an aws account, and I've recently found my rds instance is apparently in 3 subnets (subnet is listed as default with 3 subnet names underneath), one of which also has my application server. Is it necessary to have my rds in all 3 subnets? I want to move it to a separate subnet away from the application server and make it private - if that's the case is there anything in particular I will need to do?
Typically, an Amazon RDS instance is running on one server in one subnet.
However, when launching the database, you are asked to provide a Subnet Group, which identifies which subnets the database could launch in. These are typically private subnets within the VPC.
If you are using a Multi-AZ database, then it will use two subnets -- one for the Master (running) database and one for the secondary (standby) database.
It is also possible to create Read Replicas that could be in a different subnet to the Master database.
Bottom line: You are probably viewing the list of subnets in the Subnet Group that it can use, but it is likely to only be in one subnet at the moment.
I've created a VPC. By default the VPC created one public and one private subnet. I've created an additional private subnet in a different availability zone.
I then (in the ElasticCache console) created a new subnet group that contains these two private subnets from the VPC. This subnet group is also associated, of course, with the VPC.
Then, on creating an Aurora RDS within this VPC, it asks for a subnet group. There's one there, a 'default' group, but my new subnet group doesn't appear.
How do I create a subnet group that is acceptable when creating a database?
Well.. as it turns out the ElasticCache subnet groups are not visible when creating a database. You have to use the RDS console to create a 'Database Subnet Group'. Once you do that.. you're set.
ElasticCache and RDS are different types of product groups. Their SubnetGroups are different entities and they don't over lap with each other. You would need to create subnet groups in RDS to use it with RDS engines (database engines). They are not tied to any db engine, so you can re-use them within RDS.
One additional thing to note is that some other Database productions like Amazon Neptune and Amazon DocDB are able to access your RDS subnet groups as well. Just an FYI.
Given a VPC, can I not explicitly mention which subnets the RDS instance should exist?
I have created a VPC 10.0.0.0/24 with three subnets as shown below:
REST servers - 10.0.0.0/25
RDS - AZ1 - 10.0.0.128/26
RDS - AZ2 - 10.0.0.192/26
When creating the DB, I am able to provide the VPC name. It seems, all subnets of this VPC are automatically selected. I am not able to specify the two subnets (as shown in the list above). There is an option for public accessibility which I have set to No. Therefore, even though all subnets seem to be applied for this RDS instance, it seems that, it will be accessible only from the REST servers subnet.
You need to select the DBSubnet Group , which should have your private subnets.
You need to create a new subnet group and assign it while creating a new RDS. Make note that existing RDS doesn't reflect when you change the subnet group, hence you need to create a new one.
I'm trying to create my first RDS Instance... I select Create a new VPC and then on the next page it tells me:
"A VPC and DB Subnet Group are required but you do not have any compatible subnet groups for your current selection."
Why is it not recognizing the subnet group that is generated with the new vpc? I'm so confused. How can I launch my database?
From the RDS console, there is an option for "Subnet Groups" on the left. You have to pick a VPC, then an existing subnet(s), before you can deploy RDS into it.
I'm following AWS's instructions Scenario 2: VPC with Public and Private Subnets and am having issues at the point I try to launch a DB server.
When I launch my instance, all is fine and I am able to assign it to my newly created VPC. However, when it comes to launch the RDS, the only VPC available (on step 4, configure advanced settings) is the default VPC (ie not the one I created as per their instructions).
Has anyone any idea about this or indeed how to resolve it?
RDS requires a little more setup than an EC2 instance if you want to launch it within a VPC.
Specifically, you need to create:
a DB subnet group within the VPC
a VPC security group for the RDS instance
The documentation is a little buried in the AWS RDS documents. It can be found here:
Creating a DB Instance in a VPC