Re: Help... please! It's trying to kill me! (Serious EVMS problems)

Itai Tavor <[email protected]> wrote on 11/20/2006 07:43:40 AM:

> Hi...

> I got some serious problems with my server... for some reason that I
> can't figure out, things suddenly started going wrong a couple of
> days ago, and since then every time I tried to change anything,
> everything got worse...

> An example - I had a /dev/evms/duchess volume of 5GB. I created a
> new /dev/evms/nas-data volume of 200GB. I kept getting errors trying
> to access it, so I deleted it. But now, in some way I absolutely
> can't explain, nas-data is back and duchess is a compatibility volume
> (/dev/evms/lvm2/main/duchess) which has the same size and content of
> nas-data...

> Also, the biggest volume, which is a 900GB lvm2 compatibility volume
> formatted with XFS, now returns error 990 whenever I try to access it.

> The full output of evms_gather_info is at http://insentiv.net/
> evms_gather_info . Please please please could someone tell me if
> there's anything I can do to get my data back?

> TIA, Itai

Hello, Itai.

One hint of what is going wrong is at the beginning of the output of
evms_gather_info:

LVM2: The PV with index 23 was not found when discovering container
lvm2/main.
An "error" object will be created in it's place. Any regions in this
container
that map to this PV will return I/O errors if they attempt to read or write
to
this PV. Regions that don't map to this PV will work normally.

In case you are not up on your LVM terms, a PV (Physical Volume) is an
object that the volume group ("container" in EVMS terminology) comprises.
For example, in your setup sda1, sda2, sda3, sda5, sda6, sda7, sda8, sda9,
sdb2, sdb3, sdb7, sdb8, sdb9, sdc5, sdc6, sdc7, sdc8, sdc9, sdc10, sdc13,
sdd5, sdd6, sdd7, sdd8, sdd9, and sdd10 are all PVs that belong to volume
group lvm2/main.

I don't know which PV had index 23, but whichever one it is, it's missing,
which would explain why you get errors reading  volume /dev/evms/nas-data.
>From your output, part of region lvm2/main/nas-data resides on sda1 --
segment sda1 lists region lvm2/main/nas-data as one of its parents.  There
are no other segments that have region lvm2/main/nas-data as a parent.
Seeing that segment sda1 is 37.26 GB and region lvm2/main/nas-data is
200.00 GB, a good chunk of lvm2/main/nas-data is missing and is probably on
the missing PV.  The missing PV was replaced with an "error" object -- one
that returns errors whenever it is accessed.

The metadata for an EVMS volume are kept at the end of the object that is
made into the volume.  If the end of region lvm2/main/nas-data is mapped to
the error object, then EVMS will not discover the /dev/evms/nas-data volume
since it won't be able to find the metadata for the volume.  It will make a
compatibility volume instead.

A similar story could be made for volume duchess if part of region
lvm2/main/duchess was mapped to the error object for the missing PV.

On first inspection, it appears to me that your main problem is that you
are missing a disk or segment for the container lvm2/main.  The rest of the
problems can be explained as side effects of the missing PV.  Looking at
the list of PVs above, do you notice one that is missing?  The list above
was made by hand from looking at your evms_gather_info output.  For a more
accurate list run evmsn or evmsgui and see which objects container
lvm2/main consumes.  (Or run the command "q:chi,lvm2/main" in the evms
Command Line Interpreter.) The missing object is most likely at index 23 in
the LVM2 volume group.  If that object still exists, then it's likely that
the LVM2 metadata on it are corrupt.  You may be able to rebuild it by
hand, but that skill is outside my area of expertise.

Hope this helps.

Steve D.


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