[linux-lvm] Can't pvcreate /dev/sda

[Turbo Fredriksson]

This is very weird!

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root at pegasos:~# pvscan
  PV /dev/hdb   VG MovieShare   lvm2 [74.53 GB / 74.53 GB free]
  PV /dev/sdb                   lvm2 [372.61 GB]
  Total: 2 [447.14 GB] / in use: 1 [74.53 GB] / in no VG: 1 [372.61 GB]
root at pegasos:~# pvcreate /dev/sda
  Physical volume "/dev/sda" successfully created
root at pegasos:~# pvscan
  PV /dev/hdb   VG MovieShare   lvm2 [74.53 GB / 74.53 GB free]
  PV /dev/sdb                   lvm2 [372.61 GB]
  Total: 2 [447.14 GB] / in use: 1 [74.53 GB] / in no VG: 1 [372.61 GB]
----- s n i p -----

Any ideas?