[libvirt-users] KVM incremental backup using CBT

Jd jd_jedi at convirture.com
Fri Oct 10 17:37:37 UTC 2014

     Looking in to implementing (CBT like) delta backup for KVM.

     The following looks promising..(last paragraph)

      * In the last para, there is a mention of copy the blocks from the 
disk using dirty-bitmap as reference. How to accomplish this ? 
block-mirror with bitmap or is there a qemu-img command ? some details 
would be appreciated.

// backup software now reads foo.img using t0_dirty.dbmp to perform incremental backup, when finished

      * The backup after few runs in the backup store would be base 
image + bunch of delta blocks ? Will this be same as base disk and bunch 
of deltas ? or there is some special way to merge these ?

      * I am assuming this scheme (snapshot, bitmap, block merge etc.) 
should work with base disk in raw (non-qcow) format as well ? Right ? 
i.e. will it work when the storage disk is iscsi, lvm, fc ? std linux 
block device?

      * Are there libvirt-api/verbs for doing some of this or we will 
have to sue the qemu-monitor-command ?

      * What version of qemu/kvm will have the core capabilities and 
which min libvirt version would be sufficient ?

      Is there a better way to do incremental backup / CBT like backup 
than one mentioned here ?

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