> if a disk fails you'll have to go into a read-only mode during the rebuild That's not correct, you can rebuild online. The readonly mode is only relevant whe

> if a disk fails you'll have to go into a read-only mode during the rebuild That's not correct, you can rebuild online. The readonly mode is only relevant when you reboot during the failure and don't have the right options set on the volume. But you totally can replace a live drive without affecting the availability.