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
