Amazon EBS volumes come with a very cool feature called "lazy loading". In a nutshell: if a volume is created from an existing snapshot, it can become available almost immediately without waiting for all data to be restored. This allows for extremely fast provisioning of large data sets as long as you don't explicitly require the entire data set to be present before you start using it.
When an EBS volume is restored from snapshot, its blocks are fetched from Amazon S3. It happens either lazily in the background or explicitly on demand (think of a pagefault-like mechanism) and of course, fetching pieces of data from Amazon S3 is going to be one-two orders of magnitude slower than reading blocks directly from a volume.
In this short article, I will try to give you an idea of how this may impact the crash recovery time of your MySQL databases. Why talk about this? Depending on the workload and data set layout, crash recovery of a MySQL …