I thought I'd test replacing a failed drive in a 4 drive raid 10 array on a CentOS 5.2 box before it goes online and before a drive really fails. I 'mdadm failed, removed', powered off, replaced drive, partitioned with sfdisk -d /dev/sda | sfdisk /dev/sdb, and finally 'mdadm add'ed'. Everything seems fine until I try to create a snapshot lv. (Creating a snapshot lv worked before I replaced the drive.) Here's what I'm seeing. # lvcreate -p r -s -L 8G -n home-snapshot /dev/vg0/homelv Couldn't find device with uuid 'yIIGF9-9f61-QPk8-q6q1-wn4D-iE1x-MJIMgi'. Couldn't find all physical volumes for volume group vg0. Volume group for uuid not found: I4Gf5TUB1M1TfHxZNg9cCkM1SbRo8cthCTTjVHBEHeCniUIQ03Ov4V1iOy2ciJwm Aborting. Failed to activate snapshot exception store. So then I try # pvdisplay --- Physical volume --- PV Name /dev/md3 VG Name vg0 PV Size 903.97 GB / not usable 3.00 MB Allocatable yes PE Size (KByte) 4096 Total PE 231416 Free PE 44536 Allocated PE 186880 PV UUID yIIGF9-9f61-QPk8-q6q1-wn4D-iE1x-MJIMgi Subsequent runs of pvdisplay eventually returns nothing. pvck /dev/md3 seems to restore that but creating a snapshot volume still fails. It's as if the "PV stuff" is not on the new drive. I (probably incorrectly) assumed that just adding the drive back in to the raid array would take care of that. I've searched quite a bit but have not found any clues. Any one? -- Thanks, Mike