[linux-lvm] Fwd: Questions about residual data in LVM after delete the Logic Volume

[Young Yang]

---------- Forwarded message ----------
From: Young Yang <afe.young at gmail.com>
Date: Thu, Nov 26, 2015 at 4:20 PM
Subject: Questions about residual data in LVM after delete the Logic Volume
To: linux-lvm at redhat.com



Hi

This is my LVM version

stack at DevStackOSDomU:~$ sudo lvm version
>   LVM version:     2.02.98(2) (2012-10-15)
>   Library version: 1.02.77 (2012-10-15)
>   Driver version:  4.27.0


I created a 1GB physical volume with a block device setup by losetup,  and
added it to my volume group.
Then I created a 1GB logic volume  A  and  I can find my block device
here /dev/stack-volumes-lvmdriver-1/volume-e31af77b-1bf4-43e3-ac1f-23e3e825e576.

I mount this Logic volume and write some data containing a string PATTERN
 into it.
Then I grep the block device with  `sudo grep -zbl PATTERN
/dev/stack-volumes-lvmdriver-1/volume-e31af77b-1bf4-43e3-ac1f-23e3e825e576`
 and   It really have found the string  PATTERN

Then I deleted this 1GB logic volume A  and created another  1GB logic
volume.B.
I expected  the residual data containing string PATTERN should appear in
the 1GB logic volume B, because they both used all the same 1GB physical
volume.
However, when I grep the  1GB logic volume B's block device directly,  it
return nothing.



*So Here comes the quesions,*

Does LVM have any mechanism to prevent the residual data in the previously
deleted logical volume from  appearing in the new logical volume?
If there is any, how can I config it?  How  does it work , where can I find
the related  docs?




Thanks in advances  :)
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