From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [10.34.131.78] (dhcp131-78.brq.redhat.com [10.34.131.78]) by int-mx13.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id tB1AjRJa021873 for ; Tue, 1 Dec 2015 05:45:28 -0500 References: From: Zdenek Kabelac Message-ID: <565D7A46.9030002@redhat.com> Date: Tue, 1 Dec 2015 11:45:26 +0100 MIME-Version: 1.0 In-Reply-To: Content-Transfer-Encoding: 7bit Subject: Re: [linux-lvm] Fwd: Questions about residual data in LVM after delete the Logic Volume Reply-To: LVM general discussion and development List-Id: LVM general discussion and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , List-Id: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: LVM general discussion and development Dne 27.11.2015 v 13:28 Young Yang napsal(a): > > ---------- Forwarded message ---------- > From: *Young Yang* > > Date: Thu, Nov 26, 2015 at 4:20 PM > Subject: Questions about residual data in LVM after delete the Logic Volume > To: linux-lvm@redhat.com > > > > Hi > > This is my LVM version > > stack@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? Nope - lvm2 as "L"ogical "V"olume "M"anager does not zero user's data. If you do not want to 'leak' your data after use - simply 'zero' LV before it's being removed (might be quite lengthy operation) If you use 'SSD' and you have some kind of 'trust' into discard/trim - you may setup sending of discard on deleted extents (however note - you cannot revert back with 'vgcfgrestore' your LV removal operation. You could also switch into 'thin-provisioning' - which does provide 'zeroing' of new provisioned blocks - depends on your use-case - but then you are STRONGLY advised to switch to some modern distro and not 3 years old one.... And also the most secure option is - encrypt LV (dm-crypt) this way you simply don't care what does exist in blocks since without proper key data are just white noice... Regards Zdenek