On Fri, Oct 12, 2012 at 8:14 PM, Lukas Laukamp <lukas@xxxxxxxxxx> wrote: > Am 12.10.2012 13:36, schrieb Stefan Hajnoczi: > >> 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 > > > I tested the qemu-img command now, but it does not do that what I want. I > have a VM with a 5GB disk, this disk is not allocated with 1GB of data. When > I do the convert command the output is a 5GB qcow2 disk. What do I have to > do to get a qcow2 file with only the allocated space/data from the LVM? I > also tried the -c option of qemu-img convert but the result was nearly the > same. Please show the exact command-lines you are using and the qemu-img info <filename> output afterwards. 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
