FreeBSD vinum volume manager
Gvinum is an implementation of the vinum volume manager in GEOM, and it have undergone many changes since the initial import in 5.0. This page will explain some basics about gvinum as well as point out it's short-comings, and how they are addressed.
Support for using gjournal on top of gvinum volume
The problem is in PR http://www.freebsd.org/cgi/query-pr.cgi?pr=133604
The problem is also in HEAD, and will probably be fixed only there unless it turns out to be easily fixable in 7.x as well.