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From: oliver <oliver@are-b.org>
To: LVM general discussion and development <linux-lvm@redhat.com>
Subject: Re: [linux-lvm] Partition table gone? Any way to restore?
Date: Thu, 03 Mar 2005 23:28:47 +0100	[thread overview]
Message-ID: <42278F9F.4090009@are-b.org> (raw)
In-Reply-To: <1109796276.31821.263.camel@seki.nac.uci.edu>

Small update. Using a hex editor i was able to more closley examine my 
disk(s). Since I have 2 LVM setups I was somewhat able to compare what I 
have to what I should have. I do still need some insite however.

 From what I can tell, pvcreate only modifies the first few k's of the 
disk, followed by information stored from the vgcreate.
Then the lvcreate adds some more information after this. (vg00/lv basicly).

I hope i got it right so far : )

Now, the vgcreate information is identical on the two surviving parts 
except for a 'hostname<someserialnumber>' part around address 0x00012c.

Then at 0x0001000 we see the UUID of the VG passing by followed by some 
data (which is identical on all three vgs.

I don't think i have to look beyond this point in space/address.

Assuming that none of the tools (besides pvcreate) write anything before 
0x0001000, I should be able to pvcreate /dev/hde edit the UUID of that 
specific PV (to the same stored in the other two PV's so the three match 
up again) and have a fully workable LVM set again.

The only thing that might worry me is crc information stored somewhere 
after 0x0001000 (However it appears to me that there isn't a whole bunch 
of data stored before 0x0001000 and the data created by pvcreate is 
identical on all 3 drives with the exception of the UUID so the crc 
value should match again) and the string 'vg00'at 0x0000ac i see on all 
disks (the name of the vg.

What my question is (without spending days reading the sourcecode : ) is 
am I correct? Assuming that all the 'important' metadata and such is 
stored 'after' 0x0001000 hex, is there a good chance of it working?

I'm thinking of running a pvcreate, change the UUID of the PV to what I 
expect it to be, add 'vg00' at 0x000ac and be happy?

I could simply try, I know, but some feedback first would be appreciated 
; ) I really don't want to loose my data.

Thanks a lot.

Oliver

  reply	other threads:[~2005-03-03 22:28 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2005-03-02 17:45 [linux-lvm] Partition table gone? Any way to restore? oliver
2005-03-02 17:48 ` Jan-Benedict Glaw
2005-03-02 17:58   ` oliver
2005-03-02 18:05     ` Jan-Benedict Glaw
2005-03-02 19:08       ` oliver
2005-03-02 19:15         ` Jan-Benedict Glaw
2005-03-02 19:17         ` Jean-Luc Coulon (f5ibh)
2005-03-02 19:26           ` oliver
2005-03-02 19:33             ` Jean-Luc Coulon (f5ibh)
2005-03-02 20:09               ` oliver
2005-03-02 20:44           ` Dan Stromberg
2005-03-03 22:28             ` oliver [this message]
2005-03-03 22:49               ` [linux-lvm] Internal Knowlegde required. Please help me recover this sucker oliver
2005-03-03 23:04                 ` [linux-lvm] Internal Knowlegde required. Follow up oliver
2005-03-04  0:18                   ` [linux-lvm] Help! CRC Calculation how and where? oliver
2005-03-04  0:37                     ` [linux-lvm] Help! PV Size calculation etc oliver

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