[pve-devel] [Enhancement request] Thin Provisionning problems.. need to zero LVM disks before deleting a VM

Philippe OTTIN philippe.ottin at weishardt.com
Wed Mar 7 11:16:15 CET 2012

Le 07/03/2012 10:27, Dietmar Maurer a écrit :
>> It seems this problem is common on all thin-provisionning SAN's (not only
>> SanMelody)
>> I wanted to modify Storage.pm to add a the dd command before the
>> lvremove, but the problem is that is lasts from seconds to minuts... and
>> the GUI session waits for the end of the dd before allowing me to do
>> anything else..
>> Dietmar told me on the forum, that lvremove was considered as a quick
>> command, and that's why it wasn't managed on a "batch" way.
>> So my question is : is there a way to add this feature in 2.0?
>> 1) put a parameter (on the storage definition?) telling that we would
>> like to zero the LV before lvremove
> Yes, something like that. Or a global setting in datacenter.cfg
> This also seems to be a general security problem. AFAIK lvcreate and lvremove does
> not zero out data, so it is possible to one VM see data of another (deleted) VM?
> - Dietmar

Make the test
* create an 100MB LV, zero it, mkfs.ext3 it
* copy a 50M file in it
* lvremove it
* lvcreate another one with the same size

you're unable to mount it, but the data are still there...
if you hexdump of the LV : you'll find the you've copied...

More interessant, do fsck and it will rebuild the FAT...
now you're able to mount it and see the data...

There can indeed be a security problem...

Cordialement/Best regards

Philippe OTTIN
Responsable Système/System Manager
Weishardt Holding
tel: +33 5 63 42 35 04
fax: +33 5 63 42 35 15

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