[lug] LVM and software raid

Dan Ferris dan at usrsbin.com
Mon Nov 13 22:39:57 MST 2006

Sounds like your RAID isn't initializing properly.


Nick Golder wrote:
> I had software raid 5 configured as md0 and all was well.  I then
> layered on top of this LVM and things got better.  I wanted Xen so I worked on
> upgrading from a 2.6.17 kernel (debianized) to a 2.6.17-xen kernel (also
> debianized) and LVM did something strange - the PV Name has changed from
> /dev/md0 to /dev/sdc1 (sdc1 being a member of md0).  The best I can
> tell is that somehow the new kernel enumerated the hardware differently
> and that futzed up md0 and that affected LVM's PV.  But the attributes
> of the PV are still correct apart from the PV Name (this info is
> probably cached somewhere and is irrelevant):
> --- Physical volume ---
>   PV Name               /dev/sdc1
>   VG Name               vg_raid
>   PV Size               596.18 GB / not usable 0   
>   Allocatable           yes 
>   PE Size (KByte)       4096
>   Total PE              152621
>   Free PE               132141
>   Allocated PE          20480
>   PV UUID               jkHruD-mfHD-nFPJ-3W4k-DvtI-5agw-GC4FJJ
> I get this anytime I start working with the PV:
> Found duplicate PV jkHruDmfHDnFPJ3W4kDvtI5agwGC4FJJ: using /dev/sdc1 not
> /dev/sda1
> The device mapper creates /dev/mapper/vg_foo-lv_bar but fails to create
> the corresponding /dev/vg_foo/lv_bar.  md0 reports to be healthy after a
> resync. Trying to do anything with this volume reports a bad superblock 
> and I am at a loss.
> Any suggestions?

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