[linux-lvm] lvm2 confused about double UUID

malahal at us.ibm.com malahal at us.ibm.com
Mon Jul 27 13:41:09 UTC 2009

Christian Kujau [lists at nerdbynature.de] wrote:
> The subject says LVM is confused, but maybe it's me who is confused:
> I once had a PV made from a single /dev/sdb and all was well. This sdb 
> however was really a 2 disk RAID1 which is now split up, the system now 
> sees both disks, sdb and sdc. Of course, sdb and sdc still have the same 
> # blkid  | egrep 'sd[bc]'
> /dev/sdb1: UUID="1O2Tkq-9Jy8-VfuZ-uzFh-1f6v-iVBD-hcK6Vq" TYPE="lvm2pv" 
> /dev/sdc1: UUID="1O2Tkq-9Jy8-VfuZ-uzFh-1f6v-iVBD-hcK6Vq" TYPE="lvm2pv"
> I decided to continue to use the VG that was set up on the PV, but since 
> lvm comlained[0] about finding the same UUID on more than one device, I 
> tried to instruct lvm to just use sdb for the VG:
> # grep filter /etc/lvm/lvm.conf | grep -v \#
>    filter = [ "r|^/dev/sdc1$|", "r|/dev/.*/by-path/.*|", \
>               "r|/dev/.*/by-id/.*|", "a/.*/" ]
> Now everything looks fine, no more lvm warnings, vg02 seems to use sdb1, 
> exactly as I wanted:
> # pvs
>   PV         VG   Fmt  Attr PSize   PFree  
>   /dev/sda2  vg01 lvm2 a-   111.67G   9.27G
>   /dev/sdb1  vg02 lvm2 a-   931.46G 137.46G

I believe, "pvs" always rescans and just prints names it finds. It
doesn't really tell what is used. To really know what disk is really
being used, you need to get down to 'device mapper' level. Run 'dmsetup
table' and see what disks are actually used. You can post the output


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