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I think what the author means is:

> "Remember redis (in AWS) holds ephemeral data in memory"

(because EC2 machines don't persist their disk data between start/stops and a lot of people don't realize that until it is too late - hey remember that Bitcoin exchange that got bitten by this?)

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I suspect that’s what you meant but just for clarity, Instance storage does persist for reboots (which is effectively an OS reboot), but not if you stop/start (or terminate) the instance.

Correct, I've updated the comment.

Yes if you do an ordinary OS reboot the disk remains.

This was mostly applicable to older generations of EC2 instances (C3, M3, etc.)

EBS is now the default when creating an instance, and instance types of newer generations generally don't have instance store at all (except disk optimized instance types, and those with "d" in the name.)

Yeah, I think Amazon gave up on trying to communicate the meaning of ephemeral storage, and I think that's for the best tbh. It's too easy to have important data vanish that way. Something as simple as someone issuing a shutdown from the console is translated into an "instance stop" in AWS, which would purge the storage -- unfortunately often a lesson learned the hard way.

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