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0 pointsluhn9y ago0 comments

> What happens about downtime during upgrades or swapping instance sizes?

This is one of my favorite features of RDS: You can set a maintenance window and have the option to not have changes take effect until that window. So if I want to upgrade Postgres or change the instance size, I set it up and the downtime happens when I'm fast asleep and nobody is using the site.

I also think (but not 100% sure) that if you have Multi-AZ enabled, changes are done by upgrading the slave, failing over, and then upgrading the ex-master, so downtime is limited to the failover period.

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aidos9y ago

Ah ok. That's useful info about the multiAZ setup - I'll have a look into that.

In my case, we now have customers around the world so we don't get the "night time" luxury. Part of the work I'm now completing is to split the system into an accounts db and customer data db. I was thinking to dip my toe in the water by just moving the account db to RDS to see how it goes.

merb9y ago

downtime is more limited by your application. i.e. if there is a failure your connection / database pool just needs to reconnect. btw. we only have had psycopg2 pointing at it yet and that worked without a downtime. however i guess java hikaricp is as fast as that well. only "failures" will have a "small" downtime, however planned downtime is pretty/zero fast.

cwp9y ago

Yes, I've noticed this too. The AWS documentation and the console both say that the changes may take a long time to apply, but in fact the database is up for most of that time. I've done several big upgrades that had only a few seconds of downtime.

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