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Igor
Asked: 2014-12-06 02:07:43 +0800 CST

Simple scheme for backup virtual machine, which drawback of simple DD?

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We've been struggling to create the consistent scheme for backup of KVM virtual machines under Proxmox control and Ceph as storage, but still quite often during the vzdump with a snapshot the virtual machine is going down

120: dic 05 04:51:47 INFO: status: 17% (21731147776/127775277056), sparse 0% (1095598080), duration 1225, 17/16 MB/s
120: dic 05 04:52:47 ERROR: VM 120 not running
120: dic 05 04:52:47 INFO: aborting backup job
120: dic 05 04:52:47 ERROR: VM 120 not running
120: dic 05 04:52:48 ERROR: Backup of VM 120 failed - VM 120 not running

Vzdump config

vzdump 120 --quiet 1 --mode snapshot --mailto <email> --node node1 --compress lzo --maxfiles 2 --storage backup01

Some of our customer proposed us the following strategy of the backup from the inside of the virtual machine, saying "it is that simple!"

   mount /nfs/backup
   dd if=/dev/sda of=/​nfs/backup/$datetime-$virtualmachine

​ What would be your opinion on this proposal? How to explain in a simple and profound terms that this is a really bad idea? And how to remain calm and polite in this situation:?

Thank you!

backup

1 Answers

  1. No, this is not going to work because the disk /dev/sda will be changing during the dd run and you end up with an inconsistent image.

    Simpler explanation: Tell him that if you create a file towards the end of the backup, it will not be be backed up as the information where a file is located is at the beginning of the image and will not include the new file.

    Better yet: Just demonstrate it. It's easy to do and the result is usually spectacular...

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