Just for the record I'm about 98.7% sure that the root problem here was that the LVM stuff (pvcreate, vgcreate, lvcreate) was done when booted from systemrescuecd and had nothing to do with replacing a failed drive. The ouptut from 'pvcreate --version' on the systemrescuecd is: LVM version: 2.02.33 (2008-01-31) Library version: 1.02.26 (2008-06-06) Driver version: 4.13.0 And when booted from CentOS 5.2: LVM version: 2.02.32-RHEL5 (2008-03-04) Library version: 1.02.24 (2007-12-20) Driver version: 4.11.5 When [pv|vg|lv]create is done like it should have been (after booting CentOS) snapshot volume creation works as expected even after replacing a failed drive. On Thu, 17 Jul 2008, Mike wrote: > 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. >