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Re: [Linux-cluster] unformat gfs2

That is very good news! Now, about your backups... ;)

Look forward to seeing your code!


On 22/03/14 04:13 PM, Mr.Pine wrote:
Good news for all :
I successfully recoved all of my data(1.5TB) without even one bit lost!
my program tooks only 1 hour to do all the jobs on my 1.7 TB
partition.(I could not wait 100 days for my bash script to finish).

I will publish my  source code very soon for the public use.

Special thanks to Bob for the help.


On Wed, Mar 19, 2014 at 4:58 PM, Bob Peterson <rpeterso redhat com> wrote:
----- Original Message -----

Scripts is very very slow, so i should write program in c/c++.

I need some confidence about data structures and data location on disk.
As i reviewed blocks of data:

All reserved blocks (GFS2 specific blocks) start by : 0x01161970
Blocktype store location is at Byte # 8,
Type of start block of each resource group is: 2
Bitmaps are in block types 2 & 3.
In block type 2, bitmap info starts from Byte # 129
In block type 3, bitmap info starts from Byte # 25
Length of RGs are const, 5 in my volume (out put of gfs2_edit -p rindex

Is this info right?

Logic of my program seams should be like this:

Loop in device and temporary store block id of dinode blocks, and also
their bitmap locations

Change bitmap of blocks to 3 (11)

Bob, could you confirm this?


Hi Pine,

This is correct. The length of RGs is properly determined by the values
in the "rindex" system file, but 5 is very common, and is usually constant.
(It may change if you used gfs2_grow or gfs2_convert from gfs1).
The bitmap is 2 bits per block in the resource group, and it's relative
to the start of the particular rgrp. You should probably use the same
algorithm in libgfs2 to change the proper bit in the bitmaps. You can
get this from the public gfs2-utils git tree.


Bob Peterson
Red Hat File Systems

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