Saving Disk Space Across Multiple Rust Projects with sccache

I don’t know about you, but my laptop disk space is limited. Probably it’s more the limitation itself than the size of the limitation — there’s something about watching that progress bar creep toward red that makes every gigabyte feel precious. And if you’re working with multiple Rust projects, you know exactly what I’m talking about. Each Rust project creates its own target/ directory, filled with compilation artifacts, intermediate objects, and dependencies. A medium-sized project can easily consume 2-3 GB. Working on five projects? That’s 10-15 GB before you’ve even opened your IDE. The redundancy is maddening: the same dependency compiled five times, the same intermediate artifacts recreated across projects, all sitting there consuming your precious SSD real estate. Enter sccache (Shared Compilation Cache) — Mozilla’s compilation cache that can share build artifacts across projects, drastically reducing disk usage while maintaining build efficiency. What is sccache? sccache is a compiler cache that wraps around rustc (and other compilers) to cache compilation results. While many developers use it for speed — and yes, it makes rebuilds faster — its real superpower for disk-constrained developers is deduplication of compilation artifacts across projects. Think of it as a centralized warehouse for your compilation results. Instead of each project maintaining its own inventory, they all share from a common pool. How sccache Optimizes for Space Here’s the key insight: when you compile the same dependency across multiple projects, you’re often compiling identical code with identical compiler flags. sccache recognizes this and stores the result once, serving it to all projects that need it.

The space-saving flow:

Project 1 needs to compile tokio 1.35.0 with specific features
sccache intercepts the compilation request, computes a hash based on source code, compiler version, and flags
On cache miss, it compiles via rustc and stores the result
Project 2 needs the exact same tokio 1.35.0 with the same features
sccache recognizes the identical hash and serves the cached artifact — no recompilation, no additional disk usage

Setting Up sccache Installation is straightforward: cargo install sccache Then configure Cargo to use it globally by adding to ~/.cargo/config.toml: [build] rustc-wrapper = "sccache" Alternatively, set the environment variable: export RUSTC_WRAPPER=sccache For persistence across shell sessions, add it to your .bashrc, .zshrc, or equivalent. Configuring for Space Optimization By default, sccache stores cached artifacts in ~/.cache/sccache (on Linux) or ~/Library/Caches/Mozilla.sccache (on macOS). You can customize this and set cache size limits: export SCCACHE_DIR=/path/to/your/cache export SCCACHE_CACHE_SIZE="10G" # Set maximum cache size The cache size is a trade-off: larger caches mean more hits across diverse projects, but consume more space. For most developers working on 5–10 active projects, 5–10 GB is a sweet spot. Real-World Space Savings In my experience working on distributed malware detection systems with multiple Rust services: Before sccache:

5 projects × 2.5 GB average = 12.5 GB in target/ directories
Each project rebuilding common dependencies (tokio, serde, crossbeam, prost)

After sccache:

5 projects × ~1 GB = 5 GB in target/ directories
3 GB shared sccache cache
Total: 8 GB vs. 12.5 GB = 36% space savings

The savings increase with more projects sharing common dependencies. If you’re building microservices or working in a monorepo, the benefits multiply. Monitoring Your Cache sccache provides statistics to help you understand cache effectiveness: sccache --show-stats This displays:

Cache hits vs. misses
Cache size and location
Compilation requests served

For space optimization, watch your hit rate. Above 70% means you’re effectively reusing artifacts across projects. Caveats and Considerations Different compiler versions break sharing: If Project A uses Rust 1.75 and Project B uses 1.76, they can’t share artifacts. Keep your toolchain consistent across projects. Profile-specific builds aren’t shared: Debug and release builds have different compilation flags, so they’re cached separately. This is correct behavior — you wouldn’t want debug artifacts in a release build — but means the cache won’t help across profiles. Incremental compilation interacts differently: Rust’s incremental compilation stores fine-grained change tracking in the target/ directory. sccache works at a higher level (complete compilation units), so they’re complementary but serve different purposes. Beyond Local Disk: Remote Caching While this post focuses on local disk savings, sccache also supports remote storage backends (S3, Redis, GCS) for team-wide caching. This is particularly valuable in CI/CD pipelines where build agents are ephemeral and local caches don’t persist. But for the solo developer on a disk-constrained laptop, the local cache mode is perfectly sufficient and requires zero infrastructure. The Bottom Line If you’re managing multiple Rust projects and watching your disk space dwindle, sccache is a no-brainer. The setup takes five minutes, the maintenance is zero, and you’ll reclaim gigabytes of redundant compilation artifacts. More importantly, you’ll stop seeing that anxiety-inducing red progress bar quite as often. And sometimes, that peace of mind is worth more than the disk space itself.

Read the full article here: https://medium.com/rustaceans/saving-disk-space-across-multiple-rust-projects-with-sccache-6ffa95f9d0af