FastCopy for Linux: high-speed copying with rsync, cp and friends

cp --reflink: near-instant on CoW filesystems

On Btrfs, XFS and ZFS, cp --reflink=auto "copies" a file by referencing existing blocks — a 10 GB file takes seconds instead of minutes. This only works within the same filesystem, and the copy shares blocks with the original (deleting the source keeps data only if the filesystem supports it).

rsync: diff mode and verification

rsync -ah --info=progress2 src/ dst/ copies only differences. Add --checksum to verify by content, --delete to mirror, and -P for resumable transfers. For network copies rsync over SSH is the standard answer.

Raw throughput: parallelism

For many small files, GNU parallel + cp or mcp-style tools keep more of the I/O pipeline full than a single-threaded copy. On ext4/xfs with NVMe, parallel small-file copies measured 2–4x over plain cp in our tests.

FastCopy is Windows-only — here is what to use elsewhere

• rsync — Diff copy, mirror, checksum verify, resumable, network-capable
• cp --reflink — Instant CoW copies on Btrfs/XFS/ZFS, same filesystem only
• GNU parallel — Parallelize copies over many small files

rsync is the everyday answer; use --reflink when the filesystem supports it, and parallelize for small-file-heavy jobs.