I'm having a problem that sounds similar to the one described in http://lists.sistina.com/pipermail/linux-lvm/2003-February/013420.html. I lost one disk out of a four-disk VG. I'm 99% sure the disk was empty at the time. Now I can't get vgscan to recognize the VG. pvscan displays:
pvscan -- inactive PV "/dev/hdg1" is associated to unknown VG "vg" (run vgscan)
pvscan -- inactive PV "/dev/hdh1" is associated to unknown VG "vg" (run vgscan)
pvscan -- inactive PV "/dev/hdc2" is associated to unknown VG "vg" (run vgscan)
pvscan -- total: 3 [69.92 GB] / in use: 3 [69.92 GB] / in no VG: 0 
and vgscan displays:
vgscan -- ERROR "vg_read_with_pv_and_lv(): current PV" can't get data of volume group "vg" from physical volume(s)
I tried running vgcfgrestore -f /mnt/etc/lvmconf/vg.conf /dev/hdg1 (I'm running knoppix off of a CD at the moment, with my root partition mounted on /mnt) and got the response:
vgcfgrestore -- this is a backup of volume group "vg"
vgcfgrestore -- physical volume "/dev/hdg1" doesn't belong to volume group "vg"
Same result for each other disk. Any ideas how to get the three remaining disks up and running? Thanks.