go-volumes

Pure-Go block storage — a copy-on-write volume pool plus pluggable backings, with no cgo and no root.

A pool owns a flat array of fixed-size physical blocks; volumes are logical block devices carved out of it; snapshots are immutable, reference-counted captures; clones are instant, space-shared writable branches. Writes are copy-on-write, so overwriting a block shared with a snapshot allocates a fresh block and leaves the snapshot untouched — a small, ZFS-inspired alternative to LVM thin provisioning.

A tiny Device contract (ReadAt/WriteAt/Size/Sync/Close) is all a filesystem driver sees, so where the bytes live is pluggable: a local file, S3-compatible object storage, or an immutable, content-addressed OCI artifact. It pairs with go-filesystems: a Volume is exactly the block-backend shape its ext4/xfs drivers accept, so you can format and mount a real filesystem straight onto a pool volume.

Components

Module	Layer	What it does
interface	contract	The block-device Device contract every layer reads and writes through.
pool	pool	Copy-on-write volume pool — volumes, snapshots, clones; fails cleanly with ErrPoolFull.
s3	backing	S3-backed block store (pool Backing); from-scratch AWS SigV4, stdlib only.
oci	backing	Freeze a volume into an immutable, content-addressed OCI artifact; re-open read-only.

Why not LVM?

LVM thin snapshots can corrupt when the pool fills past a threshold: ext4 (or XFS) overwrites in place and assumes its blocks are durable, but the thin pool needs a new block for the copy-on-write — and if none is free, the write fails mid-operation and the filesystem/snapshot is left inconsistent.

go-volumes is built so that can't happen — see Concepts.