Hyper-V 2016 and subsequent releases include an improved virtual disk backup API called Resilent Change Tracking (RCT) conceptually similar to VMware's Change Block Tracking (CBT).
RCT is based on both WMI and native API and while a sample is available for the former , not much is available for understanding how the native RCT API can be used except for the reference documentation.
The native RCT functions and structures are part of the Virtual Storage API (virtdisk.h), in particular QueryChangesVirtualDisk plus extensions to the pre-existing OpenVirtualDisk, GetVirtualDiskInformation and SetVirtualDiskInformation.
The typical usage pattern consists in performing incremental backups by generating an RCT identifier via WMI and use that to obtain a list of changed areas in a disk. The data can be subsequently obtained by attaching the VHD / VHDX disk and read the provided areas from its phisycal mount point path.
This project includes a REST API service to obtain the RCT info from a given virtual disk and stream the data remotely over an authenticated HTTPS channel.
A Python client and CLI is available here.
cargo +nightly build --releaseGenerate X509 certificate and key:
openssl req -newkey rsa:2048 -x509 -keyout key.pem \
-out cert.pem -days 3650 -nodes -subj '/CN=localhost'Modify Rocket.toml setting the auth_key used by clients to autheticate.
The executable is located in:
target\release\rct-service.exeFor development purposes you can also just run it with:
cargo +nightly run