Tar backup on geom mirror drive

[Robert Fitzpatrick]

I am backing up a big home partition that results in 46GB tar.gz file 
directly to another FreeBSD machine via NFS and it is taking from 9:30pm 
until almost 7am the next morning. The source home partition is on a 
geom mirrored slice, could this be the reason for such a slow backup? 
The destination server is using RAID, but from the BIOS, not geom. Both 
servers are using gigabit cards through a gigabit switch.

--
Robert