On Fri, Oct 12, 2012 at 12:50 PM, Lukas Laukamp <lukas@xxxxxxxxxx> wrote: > Am 12.10.2012 12:47, schrieb Stefan Hajnoczi: > >> On Fri, Oct 12, 2012 at 12:16 PM, Lukas Laukamp <lukas@xxxxxxxxxx> wrote: >>> >>> Am 12.10.2012 12:11, schrieb Stefan Hajnoczi: >>> >>>> On Fri, Oct 12, 2012 at 11:17 AM, Lukas Laukamp <lukas@xxxxxxxxxx> >>>> wrote: >>>>> >>>>> Am 12.10.2012 10:58, schrieb Lukas Laukamp: >>>>> >>>>>> Am 12.10.2012 10:42, schrieb Stefan Hajnoczi: >>>>>>> >>>>>>> On Fri, Oct 12, 2012 at 08:52:32AM +0200, Lukas Laukamp wrote: >>>>>>>> >>>>>>>> I have a simple user question. I have a few LVM based KVM guests and >>>>>>>> wan't to backup them to files. The simple and nasty way would be to >>>>>>>> create a complete output file with dd, which wastes very much space. >>>>>>>> So I would like to create a backup of the LVM to a file which only >>>>>>>> locates the space which is used on the LVM. Would be create when the >>>>>>>> output file would be something like a qcow2 file which could be also >>>>>>>> simply startet with KVM. >>>>>>> >>>>>>> If the VM is not running you can use "qemu-img convert": >>>>>>> >>>>>>> qemu-img convert -f raw -O qcow2 /dev/vg/vm001 >>>>>>> vm001-backup.qcow2 >>>>>>> >>>>>>> Note that cp(1) tries to make the destination file sparse (see the >>>>>>> --sparse option in the man page). So you don't need to use qcow2, >>>>>>> you >>>>>>> can use cp(1) to copy the LVM volume to a raw file. It will not use >>>>>>> disk space for zero regions. >>>>>>> >>>>>>> If the VM is running you need to use LVM snapshots or stop the VM >>>>>>> temporarily so a crash-consistent backup can be taken. >>>>>>> >>>>>>> Stefan >>>>>>> -- >>>>>>> To unsubscribe from this list: send the line "unsubscribe kvm" in >>>>>>> the body of a message to majordomo@xxxxxxxxxxxxxxx >>>>>>> More majordomo info at http://vger.kernel.org/majordomo-info.html >>>>>> >>>>>> >>>>>> Hello Stefano, >>>>>> >>>>>> thanks for the fast reply. I will test this later. In my case now it >>>>>> would >>>>>> be a offline backup. For the online backup I think about a seperated >>>>>> system >>>>>> which every day makes incremental backups and once a week a full >>>>>> backup. >>>>>> The >>>>>> main problem is, that the systems are in a WAN network and I need >>>>>> encryption >>>>>> between the systems. Would it be possible to do something like this: >>>>>> create >>>>>> the LVM snapshot for the backup, read this LVM snapshot with the >>>>>> remote >>>>>> backup system via ssh tunnel and save the output of this to qcow2 >>>>>> files >>>>>> on >>>>>> the backup system? And in which format could be the incremental >>>>>> backups >>>>>> be >>>>>> stored? >>>> >>>> Since there is a WAN link it's important to use a compact image >>>> representation before hitting the network. I would use qemu-img >>>> convert -O qcow2 on the host and only transfer the qcow2 output. The >>>> qcow2 file does not contain zero regions and will therefore save a lot >>>> of network bandwidth compared to accessing the LVM volume over the >>>> WAN. >>>> >>>> If you are using rsync or another tool it's a different story. You >>>> could rsync the current LVM volume on the host over the last full >>>> backup, it should avoid transferring image data which is already >>>> present in the last full backup - the result is that you only transfer >>>> changed data plus the rsync metadata. >>>> >>>> Stefan >>>> -- >>>> To unsubscribe from this list: send the line "unsubscribe kvm" in >>>> the body of a message to majordomo@xxxxxxxxxxxxxxx >>>> More majordomo info at http://vger.kernel.org/majordomo-info.html >>> >>> >>> Hello Stefan, >>> >>> the rsync part I don't have understood fully. So to create a qcow2 on the >>> host, transfer this to the backup server will result in the weekly full >>> backup. So do you mean I could use rsync to read the LVM from the host, >>> compare the LVM data with the data in the qcow2 on the backup server and >>> simply transfer the differences to the file? Or does it work on another >>> way? >> >> When using rsync you can skip qcow2. Only two objects are needed: >> 1. The LVM volume on the host. >> 2. The last full backup on the backup client. >> >> rsync compares #1 and #2 efficiently over the network and only >> transfers data from #1 which has changed. >> >> After rsync completes your full backup image is identical to the LVM >> volume. Next week you can use it as the "last" image to rsync >> against. >> >> Stefan >> -- >> To unsubscribe from this list: send the line "unsubscribe kvm" in >> the body of a message to majordomo@xxxxxxxxxxxxxxx >> More majordomo info at http://vger.kernel.org/majordomo-info.html > > > So I simply update the full backup, which is simply a raw file which get > mounted while the backup? The image file does not need to be mounted. Just rsync the raw image file. Stefan -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
