SSDs have become fast, except in the cloud

This was a huge technical problem I worked on at Google, and is sort of fundamental to a cloud. I believe this is actually a big deal that drives peoples' technology directions.

SSDs in the cloud are attached over a network, and fundamentally have to be. The problem is that this network is so large and slow that it can't give you anywhere near the performance of a local SSD. This wasn't a problem for hard drives, which was the backing technology when a lot of these network attached storage systems were invented, because they are fundamentally slow compared to networks, but it is a problem for SSD.

According to the submitted article, the numbers are from AWS instance types where the SSD is "physically attached" to the host, not about SSD-backed NAS solutions.

Also, the article isn't just about SSDs being no faster than a network. It's about SSDs being two orders of magnitude slower than datacenter networks.

It's because the "local" SSDs are not actually physically attached and there's a network protocol in the way.

Depends on the cloud provider. Local SSDs are physically attached to the host on GCP, but that makes them only useful for temporary storage.

If you're at G, you should read the internal docs on exactly how this happens and it will be interesting.

Why would I lose all data on these SSDs when I initiate a power off of the VM on console, then?

I believe local SSDs are definitely attached to the host. They are just not exposed via NVMe ZNS hence the performance hit.

Your EC2 instance with instance-store storage when stopped can be launched on any other random host in the AZ when you power it back on. Since your rootdisk is an EBS volume attached across the network, so when you start your instance back up you're going to be launched likely somewhere else with an empty slot, and empty local-storage. This is why there is always a disclaimer that this local storage is ephemeral and don't count on it being around long-term.