Bitmaps and NBD: Building Blocks of Change Block Tracking
summary
Shows how qcow2 persistent dirty bitmaps and NBD block status let libvirt do efficient incremental backups: qcow2 stores host-visible qcow2 persistent dirty bitmaps since 2016; NBD exposes them via a NBD block status dirty-bitmap context so an external client can pull only changed clusters. Demonstrations use a 6 GB Fedora image plus a 100 MB drive, show a single small write hits four 64 KB clusters, and produce incremental files far smaller than full backups.
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chapters (4)
- 0:00Start
- 1:14Change Block Tracking
- 5:09Network Block Device (NBD) support in gemu
- 16:15Mixing backups with external snapshots
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