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0 pointsphonon9y ago0 comments

> Also, to the best of my knowledge RDS does not support a hot standby replica you can use for read-only queries

RDS has very nice Read Replicas.

http://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/USER_R...

For HA you can use High Availability (Multi-AZ).

http://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/Concep...

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7 comments · 3 top-level

dcosson9y ago· 2 in thread

But to be fair if you enable both you're paying for 3 servers total instead of 2, you can't read from the HA standby. (I'd imagine there are reasons not to do that anyway, but you don't even have the option of making that compromise to save on the cost)

illumin89y ago

With RDS Aurora, any of your read replicas can be promoted to read/write master in the event of a failure of your primary master. This happens in 10-15 seconds, and is very fast.

So, you can get the benefit of up to 15 read replicas, and not have to pay for an extra standby server that is sitting idle.

phononOP9y ago

Well, you can use the Read Replica only, and if you have an outage on the primary, promote the Read Replica to recover... (will take a few minutes though.)

In general though-- TANSTAAFL

cjbprime9y ago· 2 in thread

That said, it did take AWS a disturbingly long time to add support for Postgres read replicas.

grzm9y ago

Why disturbingly long? As opposed to frustratingly long? Or something else? What does the time it took Amazon to add such support imply to you?

cjbprime9y ago

You're welcome to read frustratingly. I didn't think hard about the word choice.

I suppose disturbingly is meant to imply "It was frustrating to me, and I think it would be frustrating to anyone in the situation of seriously using Postgres on RDS[1], and perhaps it ought to even decrease their opinion of the RDS team's ability to prioritize and ship features that are production-ready".

Does that make sense?

[1]: There was no workaround for getting a read replica. RDS doesn't allow you to run replication commands. So your options were "Don't use Postgres on RDS, or don't run queries against up-to-date copies of databases." There was never any announcement of when read replicas were coming. It was arguably irresponsible of them to release Postgres on RDS as a product and then wait a year to support read replicas, which is a core feature that other DB backends had already.

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YorickPeterse9y ago

Aha, I probably overlooked read replicas (haven't used RDS in about 1.5 years).

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