[aidos]

On that topic - what's the general feeling about RDS?

I'm running pg on ec2 with a hot standby slave. I need the postgis extension but am not doing anything particularly esoteric. Ideally I'd like to have the certainty of aws handling backups for me.

I was researching moving to RDS today and would love to hear thoughts on whether it's a good general solution or not. What happens about downtime during upgrades or swapping instance sizes?

[luhn]

> 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.

[aidos]

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.

[merb]

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.

[cwp]

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.

[rpedela]

Postgres RDS is solid and it supports PostGIS. If you have multi-AZ enabled, then downtime is typically measured in seconds even when upgrading versions or changing instance sizes. It will update one instance, automatically switch to it, and update the other one. It automatically handles backups, syncing read slaves, etc too. It is awesome in my experience.

[aidos]

I've just read about this and there are a lot of people saying they had significant downtime during upgrades ([1] one such story, but there were quite a few on stackoverflow etc).

I'm going to run some tests myself to see how well it works on my existing data (only 30GB at the moment, but it was only 20GB a month ago and is growing fairly rapidly).

[1] https://inopinatus.org/2016/02/16/notes-from-a-postgresql-rd...

[takeda]

Compared to others my experience with RDS is bad, although I used it last year ago perhaps things improved.

One major issues is that you are restricted to what you can do with it, not all options are available. You can only use extensions that they provide. (this I'm a bit fuzzy about) but changing disk size made service unavailable for ~30 minutes (proportional to new disk size). You weren't able to configure replication, the replication only happens to the backup node. You weren't even able to set up replication across regions.

The replication is kind of a bummer, because if you ever would like to move your data (perhaps to a vm or outside of aws) you would need to have an outage. Also if I remember there was no way to do major version update in place.

There was also another incident (it was caused by bug so hopefully it was fixed and won't happen to anyone else). We had cluster set up with a backup. One day out of nowhere the service stopped working and was unavailable for 1.5 hours. That was quite big issue because we used it for monitoring (zabbix), so any outage makes us blind to issues. Turned out that due to bug their backup routine made a mistake and started doing backup on the master server (normally it supposed to do on slave).