Unfortunately Areca is really the only controller I've found which is well supported and does RAID6 fast.
I have nothing against colo but I don't really have time to run around the country checking on servers.
Amazon is not cheap, and they have failed way too many times in recent memory.
But the api, oh the api - it's crack, and I can't live without it.
We pay a lot to stay multi-AZ and it seems Amazon keep finding ways to show us their single points of failures.
Similar thing happened to me a while ago with a vendor. When your management team summons you to ask why the hell their site is down, you can't point fingers at the vendor if their marketing literature says it doesn't go down.
Multi-AZ RDS does synchronous replication to the standby instance -- I'm guessing something broke in there. Hopefully AWS will update with a post mortem as they usually do. Lots of frustrated MultiAZ RDS customers on their forums.
Maybe there was something bad with your replication server before the outage? It's hard to guess without knowing exactly what was happening at the time...
The whole point is to protect you from problems in one AZ by keeping a hot standby in another AZ. It doesn't matter whether it's due to EBS, power, etc. This is one of the primary reason to use RDS instead of running MySQL yourself on an instance.