pvcreate not working: can't open exclusively
Solution 1:
Maybe device-mapper is 'stealing' this device. Try this:
[root@host ~]# dmsetup ls
sdb (253, 2)
VolGroup00-LogVol01 (253, 1)
VolGroup00-LogVol00 (253, 0)
If you find sdb device listed as above example, remove it using dmsetup and create the physical volume:
[root@host ~]# dmsetup remove sdb
[root@host ~]# pvcreate /dev/sdb
Physical volume "/dev/sdb" successfully created