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Re: [linux-lvm] LVM Snapshot/XFS caused system hang/VG corruption



Theo,

In order to restore your metadata for VG "t" to a sane state, you need to run:

pvcreate -ff /dev/sda4 # you need to repeat this

# needed to get rid of the snapshot
vgcfgrestore -n t -f /etc/lvmconf/t.conf.1.old /dev/sda4

vgscan # was missing!



Your assumption IRT messy minors is right (both grop files have the same
major/minor and therefore the tools access the very same VG "kluge")
and vgscan fixes that.
Maybe you need to restore from an older metadata backup file using
"vgcfgrestore -f /etc/lvmconf/t.conf.2.old -n t /dev/sda4" in order to get
rid of the messy snapshot metadata. You can have a look at the backup file
contents with "vgcfgrestore -n t -f /etc/lvmconf/t.conf.2.old -ll" and check,
if it doesn't contain the snapshot or if you need to use an older one.

Please remember to take actual backups of /etc/lvmconf/ in order to make
sure, that you have all metadata backup files at hand in case something
goes wrong. I presume that you have backups for the rest anyway ;-)

Regards,
Heinz    -- The LVM Guy --


On Fri, Jan 11, 2002 at 11:00:34PM -0500, Theo Van Dinter wrote:
> As I am planning to put LVM/XFS into place on my "production" system in the
> next few weeks, I decided to start playing around with things like snapshots.
> Unfortunately, my first attempt to create a snapshot failed miserably and the
> machine locked up cold:
> 
> # pvcreate /dev/sda4
> # vgcreate t /dev/sda4
> # lvcreate -n 1 -L 1G t
> # mkfs -t xfs /dev/t/1
> # mount /dev/t/1 /mnt/test
> # <put some data on /mnt/test>
> # lvcreate -s -n 1.snap -L 1G /dev/t/1
> # mount -t xfs -o ro,nouuid,norecovery /dev/t/1.snap /mnt/testsnap
> 
> At this point, everything was mounted and things looked good.  Then I tried
> to write some more data to /mnt/test, and the machine locked up cold.  After
> rebooting, the VG "t" won't activate:
> 
> # vgchange -a y t
> vgchange -- ERROR "parameter error" setting up snapshot copy on write
> exception table for "/dev/t/1.snap"
> 
> 
> 
> In a quick google/lvm-archive search, I've found that the suggested solution
> is to recover the backup metadata file:
> 
> # vgcfgrestore -n t /dev/sda4
> vgcfgrestore -- VGDA for "t" successfully restored to physical volume
> "/dev/sda4"
> # vgchange -a y t
> vgchange -- volume group "t" already active
> # lvscan
> lvscan -- ACTIVE            "/dev/kluge/swap" [128.00 MB]
> lvscan -- ACTIVE            "/dev/kluge/var" [128.00 MB]
> lvscan -- ACTIVE            "/dev/kluge/mp3s" [9.49 GB]
> lvscan -- ACTIVE            "/dev/kluge/swap" [128.00 MB]
> lvscan -- ACTIVE            "/dev/kluge/var" [128.00 MB]
> lvscan -- ACTIVE            "/dev/kluge/mp3s" [9.49 GB]
> lvscan -- 6 logical volumes with 19.48 GB total in 2 volume groups
> lvscan -- 6 active logical volumes
> 
> 
> So I'm now missing the non-snapshot volume in VG "t", and the other LVs I
> have in a different VG are listed twice.  After doing some investigation
> ("vgdisplay -v kluge"), I found that there are, in fact, only 1 of each in
> VG kluge, and via "vgdisplay -v t", all three are listed there too:
> 
> # vgdisplay -v t
> --- Volume group ---
> VG Name               kluge
> VG Access             read/write
> VG Status             available/resizable
> VG #                  1
> MAX LV                255
> Cur LV                3
> Open LV               3
> MAX LV Size           255.99 GB
> Max PV                255
> Cur PV                1
> Act PV                1
> VG Size               13.48 GB
> PE Size               4.00 MB
> Total PE              3450
> Alloc PE / Size       2493 / 9.74 GB
> Free  PE / Size       957 / 3.74 GB
> VG UUID               YbiqZe-PRyl-xzg9-oEuD-lmgs-r8xt-3tE7Qy
> 
> --- Logical volume ---
> LV Name                /dev/kluge/swap
> VG Name                kluge
> LV Write Access        read/write
> LV Status              available
> LV #                   2
> # open                 1
> LV Size                128.00 MB
> Current LE             32
> Allocated LE           32
> Allocation             next free
> Read ahead sectors     120
> Block device           58:2
> 
> --- Logical volume ---
> LV Name                /dev/kluge/var
> VG Name                kluge
> LV Write Access        read/write
> LV Status              available
> LV #                   3
> # open                 1
> LV Size                128.00 MB
> Current LE             32
> Allocated LE           32
> Allocation             next free
> Read ahead sectors     120
> Block device           58:3
> 
> --- Logical volume ---
> LV Name                /dev/kluge/mp3s
> VG Name                kluge
> LV Write Access        read/write
> LV Status              available
> LV #                   4
> # open                 1
> LV Size                9.49 GB
> Current LE             2429
> Allocated LE           2429
> Allocation             next free
> Read ahead sectors     120
> Block device           58:4
> 
> 
> --- Physical volumes ---
> PV Name (#)           /dev/hda4 (1)
> PV Status             available / allocatable
> Total PE / Free PE    3450 / 957
> 
> 
> And looking in the /dev/t area:
> 
> dilbert  10:55pm  [/dev/t/] # ls -la /dev/t
> total 172
> dr-xr-xr-x    2 root     root           39 Jan 11 22:46 .
> drwxr-xr-x   19 root     root        98304 Jan 11 22:46 ..
> brw-rw----    1 root     disk      58,   3 Jan 11 22:46 1
> brw-rw----    1 root     disk      58,   4 Jan 11 22:46 1.snap
> crw-r-----    1 root     disk     109,   1 Jan 11 22:46 group
> 
> 
> 
> So things are confused.  I'm not 100%, but I'm thinking it's related to
> conflicting major/minor numbers:
> 
> dilbert  10:56pm  [/dev/t/] # ls -la /dev/kluge/
> total 172
> dr-xr-xr-x    2 root     root           50 Jan 11 22:30 .
> drwxr-xr-x   19 root     root        98304 Jan 11 22:46 ..
> crw-r-----    1 root     disk     109,   1 Jan 11 22:30 group
> brw-rw----    1 root     disk      58,   4 Jan 11 22:30 mp3s
> brw-rw----    1 root     disk      58,   2 Jan 11 22:30 swap
> brw-rw----    1 root     disk      58,   3 Jan 11 22:30 var
> 
> 
> 
> There are no log entries after the snapshot mount and before the hard
> reboot, and there are no log entries about the "recovery".
> 
> So, what to do now?  I can't deactivate VG "t" because it thinks it has 3
> active LVs.
> 
> I'm running LVM 1.0.1-rc4, kernel 2.4.9-13SGI_XFS_1.0.2, on an Athlon-based
> system.  The test VG is stored on a new 3ware RAID card.
> 
> 
> Thanks. :)
> 
> -- 
> Randomly Generated Tagline:
> "As I uploaded the resultant kernel, a specter of the holy penguin
>  appeared before me, and said "It is Good. It is Bugfree". As if wanting
>  to re-assure me that yes, it really =was= the holy penguin, it finally
>  added "Do you have any Herring?" before fading out in a puff of holy
>  penguin-smoke." - Linus Torvalds
> 
> _______________________________________________
> linux-lvm mailing list
> linux-lvm sistina com
> http://lists.sistina.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://www.sistina.com/lvm/Pages/howto.html

*** Software bugs are stupid.
    Nevertheless it needs not so stupid people to solve them ***

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Heinz Mauelshagen                                 Sistina Software Inc.
Senior Consultant/Developer                       Am Sonnenhang 11
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                                                  Germany
Mauelshagen Sistina com                           +49 2626 141200
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