On Fri, 4 Sep 2020, Tomas Dalebjörk wrote: > hi > I tried to perform as suggested > # lvconvert —splitsnapshot vg/lv-snap > works fine > # lvconvert -s vg/lv vg/lv-snap > works fine too > > but... > if I try to converting cow data directly from the meta device, than it doesn’t work > eg > # lvconvert -s vg/lv /dev/mycowdev > the tool doesn’t like the path > I tried to place a link in /dev/vg/mycowdev -> /dev/mycowdev > and retried the operations > # lvconveet -s vg/lv /dev/vg/mycowdev > but this doesn’t work either > > conclusion even though the cow device is an exact copy of the cow > device that I have saved on /dev/mycowdev before the split, it wouldn’t > work to use to convert back as a lvm snapshot > > not sure if I understand the tool correctly, or if there are other > things needed to perform, such as creating virtual information about the > lvm VGDA data on the first of this virtual volume named /dev/mycowdev AFAIK LVM doesn't support taking existing cow device and attaching it to an existing volume. When you create a snapshot, you start with am empty cow. Mikulas > let me know what more steps are needed > > beat regards Tomas > > Sent from my iPhone > > On 7 Nov 2019, at 18:29, Tomas Dalebjörk <tomas.dalebjork@xxxxxxxxx> wrote: > > Great, thanks! > > Den tors 7 nov. 2019 kl 17:54 skrev Mikulas Patocka <mpatocka@xxxxxxxxxx>: > > > On Tue, 5 Nov 2019, Tomas Dalebjörk wrote: > > > Thanks, > > > > That really helped me to understand how the snapshot works. > > Last question: > > - lets say that block 100 which is 1MB in size is in the cow device, and a write happen that wants to something or all data on that region of block > 100. > > Than I assume; based on what have been previously said here, that the block in the cow device will be overwritten with the new changes. > > Yes, the block in the cow device will be overwritten. > > Mikulas > > > Regards Tomas > > >
_______________________________________________ linux-lvm mailing list linux-lvm@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
