[vacri]

I don't know about RDS psql, but RDS mysql multi-AZ does have up to 2 mins downtime when switching masters. We see that when scaling up our staging for loadtesting.

I agree on the IOPS - just get a larger disk (min 100G) even if you'll never use it. Storage is cheap. It's supposed to give you 3k IOPS but doesn't actually give you anywhere near that (but it is still fast). If you do need guaranteed IOPS, then it's wallet-opening time.

[philliphaydon]

I tested 9.4 ages ago by polling a table. Upgraded the instance type while in multi az. The down time was about ~14 seconds.

With SQL server it was about ~50seconds.

2 minutes seems like a Long time but I'm curious now and want to test this again and maybe blog about it.

[vacri]

I haven't tried for a while - my method for outage detection was simply trying to make a connection. It wasn't always 2 min, but usually somewhere between 1-2 min (never more, though).