How EBS snapshots going to be consistent? I mean AWS takes them at random time, a half of a write may be captured. Another, less common scenario is silent data corruption you never notice until you need to restore.
I assume they do the snapshotting from some script. (Stop writes, flush, snapshot, restart writes.) If not, then they probably have some way of detecting partial writes. It seems that they do fsync() every second.
> Another, less common scenario is silent data corruption you never notice until you need to restore.
I tried to find what kind of guarantees EBS offers, but they only talk about durability and availability ( https://aws.amazon.com/ebs/sla/ ), nothing about data corruption, individual sector failure. (So this could mean that they either won't even notice ... or you might get back a full zero page - assuming they detect some underlying error, but due to encryption at rest the internal checksum fails, assuming there is one.)
