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Changed-block tracking and differential backups in QEMU
- philsnow 6y ago> The network block device (NBD) protocol was first introduced 23 years ago (Linux 2.1.55; April 1997), as a way to access block devices over a network. In ~2002 I scraped together enough money (in college at the time) to replace my desktop. I bought a case/motherboard/cpu, but didn't have enough to buy lots of memory for the new machine (which didn't use the same memory as my old one), so I had 128MB on the new one and ~800MB cobbled together from various dimms on the old one. Then I read about NBD. Half an hour later I had made a 640MB ramdisk on the old machine and mounted it with NBD on the new machine, and used it as a swap disk. I couldn't believe how well it worked. Fun times.
- generalizations 6y agoGreat story. After you pointed out the NBD protocol I went and looked it up. Wish I'd learned about it a couple years ago! Found this gem on the libguestfs readme: > Well-documented, simple plugin API with a stable ABI guarantee. Lets you export “unconventional” block devices easily. I really want to know what they think "unconventional" block devices are. Could lead to some interesting projects!
- philsnow 6y agoIf you're interested in this kind of thing, 9p is also used for exporting storage over the network. https://en.m.wikipedia.org/wiki/9P_(protocol) https://en.m.wikipedia.org/wiki/9P_(protocol)
- generalizations 6y ago9p is awesome.
- fsh 6y agoThe new Proxmox Backup Server uses this feature for backing up VM images. In our setup this has accelerated daily backups by an order of magnitude.