If fsync is turned back on and a manual sync call is issued before considering the replica valid there will be no risk from this.
ants_a is correct. Also, our NVMe storage is ephemeral so you aren't recovering from a power loss anyways :)
Disclaimer: I work at AWS, not on EC2.
Locally attached disks are not ephemeral to instance reboots/power failures. However, the disks are wiped after instance terminations. On the official EC2 product pages this is called "instance storage" not "ephemeral storage."
TIL, this is really good to know! Do you know offhand if this is a new feature, or have I just always been wrong
I'm curious how much risk of data loss this added.
I guess the baseline is "we need to migrate before we run out of disk" I.e. you're either going to have data loss or a long period of unavailability if the migration cannot be carried out fast enough.