EBS seems to be the main problem here, I'll cite a former reddit employe (first comment on the blog that talked about EBS problems).

I don't work for reddit anymore (as of about a week ago, although I didn't get as much fanfare as raldi did), but I can tell you that they're giving Amazon too much credit here. Amazon's EBSs are a barrel of laughs in terms of performance and reliability and are a constant (and the single largest) source of failure across reddit. reddit's been in talks with Amazon all the way up to CIOs about ways to fix them for nearly a year and they've constantly been making promises that they haven't been keeping, passing us to new people (that "will finally be able to fix it"), and variously otherwise been desperately trying to keep reddit while not actually earning it.

Source: http://www.reddit.com/r/blog/comments/g66f0/why_reddit_was_d...

cache: - scroll down for comment - http://webcache.googleusercontent.com/search?q=cache:cfbs-sp...

EC2 instances only have one network interface. The public IP address you have pointing to your instance is a DNAT done somewhere further up the chain.

If you get a large network load to your instance - say, a DDoS attack - you can find you no longer have enough network capacity to talk to your EBS disks.

This is what happened to Bitbucket in 2009: http://blog.bitbucket.org/2009/10/04/on-our-extended-downtim...

This doesn't appear to be the issue here, though. valisystem's link mentions that it wasn't an interface issue, EBS is just shit, apparently.

Slightly offtopic, but wasn't that post by an ex-employee as a comment? Not that the technical aspect of it wasn't fantastic, because it was, but I don't think Reddit said anything publically did they?

It was, you are right, I misremembered. valisystem's comments above contains the reference.

Yes valisystem linked to it. All good, I wasn't sure if I misremembered.