[linux-lvm] LVM pretends it has more space than it actually has
Gijs
info at bsnw.nl
Wed Sep 21 18:32:28 UTC 2011
Unfortunately I can't find all the old LVM configs that the system used.
I was in the process of moving my root filesystem to the raid-5 array.
Since I needed the root to be unmounted for that, I used a FC15
USB-bootable rescue system to do the copying of the root to the raid-5
array. And that's when things went wrong. Since the rescue system is
pretty much run from memory, I don't have the LVM configs that were
created when I was using the rescue system. I do have older configs that
were created when I was creating the raid-5 array on the system itself,
but those don't show anything wrong from what I can see. (and I guess
that's correct, since nothing was wrong at that time)
I tried assembling/recreating an array on the PV-device, but that just
gave me the error "mdadm: no raid-devices specified." So I can't really
find an array on the LVM devices either.
Some info I got from the PV:
[root at poseidon ~]# pvdisplay -m /dev/md127
--- Physical volume ---
PV Name /dev/md127
VG Name raid-5
PV Size 3.64 TiB / not usable 0
Allocatable yes
PE Size 4.00 MiB
Total PE 952919
Free PE 5252
Allocated PE 947667
PV UUID ZmJtA4-cZBL-kuXT-53Ie-7o1C-7oro-uw5GB6
--- Physical Segments ---
Physical extent 0 to 714687:
Logical volume /dev/raid-5/data
Logical extents 0 to 714687
Physical extent 714688 to 714933:
FREE
Physical extent 714934 to 714953:
Logical volume /dev/raid-5/data
Logical extents 947647 to 947666
Physical extent 714954 to 719959:
FREE
Physical extent 719960 to 952918:
Logical volume /dev/raid-5/data
Logical extents 714688 to 947646
The empty spaces inbetween are from LVs there were created before. And
the 3rd segment is from when I tried to resize the data-LV to see if
that made any difference. It obviously didn't since it was the PV that
was actually too small, not the LV, which I figured out later.
From what you say, it indeed sounds like I messed up some command that
caused an array to be created on an LV, but I can't really find any
evidence that I really did that. Is there any other explanation that LVM
is acting this way? Is it perhaps possible to tell LVM to run of the
configuration stored in /etc/lvm, instead of the metadata embedded on
the PV?
There's also something that I don't understand. Why is it just the
data-LV? I had a swap and root LV as well, and those activated just
fine. Why would LVM have trouble activating the data-LV when it had no
trouble activating the swap/root-LV?
On 19-9-2011 22:41, Ray Morris wrote:
> First, if at all possible make a copy of the underlying block
> device using dd or dd_rescue. Very often the most severe damage
> is done during the attempt at recovery.
>
> Then let's find the oldest back up copies on the LVM meta data to
> see if we can verify how things were set up when they were working.
> This will find metadata over 50 days old:
>
> find /etc/lvm/archive -mtime +50
>
> mainly what we're looking for is to see if any mdadm RAID devices
> were used as PVs at some point.
>
> Next try mdadm --assemble --readonly --assume-clean /dev/sdFOO to see
> if you can assemble an array using the lower level device (which is
> also marked as a PV right now). If it assembles, do:
> pvdisplay -m /dev/md0
> to see if it's a PV, and check to see if it has a filesystem.
>
> Based on the messages you got, it looks like /dev/md0 at one point
> was the PV, rather than being assembled from LVs.
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