I am in the process of planning a file server for private usage (small amounts of various kinds of data, but mainly photos, videos, music). I will probably use NAS4free/FreeNAS and want to give ZFS a try.
My focus is not speed, it is reliability and data safety. Nevertheless, I want to keep things 'cheap', so I want to run ZFS mirrored among two disks ('raid 1' fashion). I will buy a consumer board, so no hardware raid controller. So far, I am thinking to use the ZFS 'mirror' command for this or whatever corresponding option FreeNAS provides.
When reading about this topic, I mainly see people using three disks and then using RAIDZ-1 which renders them immune in case one disk fails. What I do not quite understand so far is what is the problem with having ZFS mirrored among two disks only? How will I notice when one disk fails? What is the failover strategy? Do I just get a message that the file system is not usable, because disk A is failing and that I should replace it now? I hope that one can achieve a real benefit when running two mirrored disks than just using one.
Given two equivalent disks, which ZFS mode would you run in?