AWS Certified Solutions Architect - Professional 2020

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Why is RDS is shown in the persistent data store and not EBS/EFS?

In section 2.2 of this SA PRO video, I see RDS and Glacier mentioned in the persistent data store. I strongly don’t agree with keeping RDS over there as it uses EBS in the backend, which should have been mentioned.

2 Answers

I think these are just examples, not a comprehensive list.

EBS being used in the backend is an implementation detail of the RDS service(s) that doesn’t really make much of a difference in this case. The point being made about storage using these examples is that there are three main classifications of storage: Persistent (will survive a machine reboot), Transient (data exists, but does not stay here at rest), and Ephemeral (as soon as the data is flushed from active memory, it’s gone forever).

In this sense, EBS is also a persistent data store because an EBS volume is not deleted upon detaching from an instance (although, you can delete it when detached, it’s not the default). I think there may be some confusion here about what Persistent means, particularly a mix up with durable storage … but that is a discussion for another day 🙂

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