That post ("Amazon EC2 + S3 Doesn't Cut it for Real Applications") contains a false statement which the author has not corrected, even though commenters there quickly pointed out its falsehood. The falsehood is: "There is no persistent storage in EC2 so if your virtual server goes down for any reason such as taking it down to install security patches or a system crash, all your data is lost."
Instances can reboot, under operator control or due to a crash, and still retain their existing hard drive storage. Only less frequent 'instance termination' causes a loss of hard drive contents.
True, there are no guarantees that any instance won't be terminated by Amazon or other system failures at any time, so you're supposed to have your own backup and persistence strategy. But in practice, full terminations are rare, and Amazon has even given warnings when system upgrades mean large instance turnover is expected. (Though, there is no guarantee they will do so.)
So the falsehoods above are "[data is lost] if your virtual server goes down for any reason" and both concrete examples given, "taking it down to install security patches" and "system crash".
Three days ago I received an email from Amazon alerting me that "one or more of your instances are running on hosts degraded due to hardware failure.", and giving me a week to migrate to another instance. I have a script that creates daily instance images as a back-up procedure, so the "migration" was just a matter of starting another instance using the most recent image and I was up and running.
I looked back on my logs and found out that the particular degraded instance was running since June without any problems or shutdowns. Not bad for a VPS...
I'm very aware that Amazon provides no guarantees, but I have to say that my confidence on EC2 increased after this incident.
From reading the comments, it's kind of difficult to figure out what gets persisted and what doesn't. I mean, if it's persistent until you shut the machine down, that's not so bad... it's like having a VPS somewhere, no?
The local storage is persistent until Amazon shuts down the virtual machine whenever they want. (They say that it only happens due to hardware failures or EC2 platform upgrades, but you have no control over those events.)
