Re: Help restoring a corrupted PV partition ( 18th )

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Dne 18. 10. 21 v 20:08 Brian McCullough napsal(a):

I have had a disk go bad on me, causing me to lose one PV.

If I am not providing sufficient, or the proper, information, feel free
to ask for more.


I seem to have retrieved the partition using ddrescue and put it on to
a new drive, but it seems to be missing some label information, because
pvscan doesn't recognize it as a PV partition.

Using hexdump, I see the string " LVM2 " at 0x1004, but nothing before
that.  The whole 16 bytes is:

0x01000  16 d6 8e db 20 4c 56 4d  32 20 78 5b 35 41 25 72
                         L  V  M  2



I find what appears to be an LVM2 vgconfig block starting at 0x01200,
extracted that to a file and was able to read the UUID that this PV
should have.  It is one of about a dozen that make up this VG.


On another machine, I dumped a PV partition, and find "LABLEONE" at
0x200, with the same " LVM2 " at 0x01000.

I was concerned that my dump was offset, but the comparison to the
"good" one suggests that that isn't the problem, but just the missing
"LABLEONE" and related information at 0x0200.


How to fix?

If I do a "pvcreate --uuid xxxx" would this fix that recovered partition
so that pvscan and friends can work properly, and I can finally boot
that machine?

Hi

It's quite important to be aware how the disk corruption happened.
Was this plain disk hw error -  or some crash of raid setup ?

Normally you could restore PV with this:

pvcreate --uuid  XXXX --restorefile  file_with_vg_backup  /dev/ddddd
vgcfgrestore --restorefile   file_with_vg_backup   vgname


But if the content of device was scramble by some 'raid' bug - you might have problem to retrieve any usable data afterward.


Regards

Zdenek

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