This repository contains tools for synching and streaming files. They are based on Content Defined Chunking (CDC), in particular FastCDC, to split up files into chunks.
CDC RSync is a tool to sync files from a Windows machine to a Linux device, similar to the standard Linux rsync. It is basically a copy tool, but optimized for the case where there is already an old version of the files available in the target directory.
- It skips files quickly if timestamp and file size match.
- It uses fast compression for all data transfer.
- If a file changed, it determines which parts changed and only transfers the differences.
The remote diffing algorithm is based on CDC. In our tests, it is up to 30x faster than the one used in rsync (1500 MB/s vs 50 MB/s).
CDC Stream is a tool to stream files and directories from a Windows machine to a Linux device. Conceptually, it is similar to sshfs, but it is optimized for read speed.
- It caches streamed data on the Linux device.
- If a file is re-read on Linux after it changed on Windows, only the differences are streamed again. The rest is read from cache.
- Stat operations are very fast since the directory metadata (filenames, permissions etc.) is provided in a streaming-friendly way.
To efficiently determine which parts of a file changed, the tool uses the same CDC-based diffing algorithm as CDC RSync. Changes to Windows files are almost immediately reflected on Linux, with a delay of roughly (0.5s + 0.7s x total size of changed files in GB).
The tool does not support writing files back from Linux to Windows; the Linux directory is readonly.
The project has to be built both on Windows and Linux.
The following steps have to be executed on both Windows and Linux.
- Download and install Bazel from https://bazel.build/install.
- Clone the repository.
git clone https://github.com/google/cdc-file-transfer
- Initialize submodules.
cd cdc-file-transfer git submodule update --init --recursive
Finally, install an SSH client on the Windows device if not present.
The file transfer tools require ssh.exe
and scp.exe
.
The two tools can be built and used independently.
- Build Linux components
bazel build --config linux --compilation_mode=opt //cdc_rsync_server
- Build Windows components
bazel build --config windows --compilation_mode=opt //cdc_rsync
- Copy the Linux build output file
cdc_rsync_server
frombazel-bin/cdc_rsync_server
on the Linux system tobazel-bin\cdc_rsync
on the Windows machine.
- Build Linux components
bazel build --config linux --compilation_mode=opt //cdc_fuse_fs
- Build Windows components
bazel build --config windows --compilation_mode=opt //asset_stream_manager
- Copy the Linux build output files
cdc_fuse_fs
andlibfuse.so
frombazel-bin/cdc_fuse_fs
on the Linux system tobazel-bin\asset_stream_manager
on the Windows machine.
To copy the contents of the Windows directory C:\path\to\assets
to ~/assets
on the Linux device linux.machine.com
, run
cdc_rsync --ssh-command=C:\path\to\ssh.exe --scp-command=C:\path\to\scp.exe C:\path\to\assets\* user@linux.machine.com:~/assets -vr
Depending on your setup, you may have to specify additional arguments for the ssh and scp commands, including proper quoting, e.g.
cdc_rsync --ssh-command="\"C:\path with space\to\ssh.exe\" -F ssh_config_file -i id_rsa_file -oStrictHostKeyChecking=yes -oUserKnownHostsFile=\"\"\"known_hosts_file\"\"\"" --scp-command="\"C:\path with space\to\scp.exe\" -F ssh_config_file -i id_rsa_file -oStrictHostKeyChecking=yes -oUserKnownHostsFile=\"\"\"known_hosts_file\"\"\"" C:\path\to\assets\* user@linux.machine.com:~/assets -vr
Lengthy ssh/scp commands that rarely change can also be put into environment
variables CDC_SSH_COMMAND
and CDC_SCP_COMMAND
, e.g.
set CDC_SSH_COMMAND="C:\path with space\to\ssh.exe" -F ssh_config_file -i id_rsa_file -oStrictHostKeyChecking=yes -oUserKnownHostsFile="""known_hosts_file"""
set CDC_SCP_COMMAND="C:\path with space\to\scp.exe" -F ssh_config_file -i id_rsa_file -oStrictHostKeyChecking=yes -oUserKnownHostsFile="""known_hosts_file"""
cdc_rsync C:\path\to\assets\* user@linux.machine.com:~/assets -vr