What release of Debian, and what version of "lvm2" are you using?
My FAI server: # cat /etc/debian_version 6.0.3 # dpkg --list | grep lvm2 ii lvm2 2.02.66-5 The Linux Logical Volume Manager # uname -a Linux fai0 2.6.32-5-686 #1 SMP Thu Nov 3 04:23:54 UTC 2011 i686 GNU/Linux # dpkg --list | grep fai ii fai-client 3.4.8 Fully Automatic Installation client package ii fai-doc 3.4.8 Documentation for FAI ii fai-quickstart 3.4.8 Fully Automatic Installation quickstart package ii fai-server 3.4.8 Fully Automatic Installation server package ii fai-setup-storage 3.4.8 automatically prepare storage devices System installed by FAI: # cat /etc/debian_version 6.0.5 # dpkg --list | grep lvm2 ii lvm2 2.02.66-5 The Linux Logical Volume Manager # uname -a Linux opsi1 2.6.32-5-686 #1 SMP Sun May 6 04:01:19 UTC 2012 i686 GNU/Linux