About RAIDZ geometry

[cooper]

Hi folks,

Now that ZFS has been ported to FreeBSD, I think it's proper to ask
these questions in this mailing list.

Is there any detailed documentation about RAIDZ geometry? I has been
wandering how zfs remembers which disk sectors are for data and which
ones are for parity.

They claimed "Every block is its own RAID-Z stripe" does that mean zfs
writes exactly one block in every vdev_raidz_io_start if the io type of
the zio is write?

And also claimed "You have to traverse the filesystem metadata to
determine the RAID-Z geometry" where is this metadata stored?