19. Performance
August 3, 2026 · View on GitHub
Numbers from script/fs-bench.sh and a full
npm install of cloudflare/sandbox-sdk
(854 packages, 36,675 files), running
examples/container on a Cloudflare
Containers standard-2 instance (1 vCPU, 6 GiB memory, 12 GB disk).
The computerd FUSE mount lives at /workspace; the comparison columns are
an in-memory tmpfs at /tmp and the container's ext4 root disk at
/var/tmp.
Ratios are computerd / baseline — lower is faster, values below 1.0 mean
computerd beats the baseline.
fs-bench (REPS=3, WARMUP=1, randomized targets)
| Scenario | computerd | tmpfs | tmpfs ratio | ext4 disk | disk ratio |
|---|---|---|---|---|---|
| tiny-file churn | |||||
| create 1000 files | 560.6 ms | 83.2 ms | 6.7x | 303.2 ms | 1.85x |
| stat 1000 files | 1971.9 ms | 1324.2 ms | 1.49x | 2659.3 ms | 0.91x |
| rm 1000 files | 827.7 ms | 322.7 ms | 2.56x | 1281.8 ms | 0.66x |
| directory traversal | |||||
| mkdir tree (10×10×10) | 1597.5 ms | 1585.7 ms | 1.01x | 3034.7 ms | 0.74x |
| find tree | 1813.6 ms | 1819.9 ms | 1.00x | 4404.2 ms | 0.72x |
| large file I/O | |||||
| write 64 MiB | 230.6 ms | 47.3 ms | 4.87x | 16.8 ms | 16.93x |
| copy 64 MiB | 1037.2 ms | 37.4 ms | 27.75x | 39.8 ms | 40.46x |
| read 64 MiB | 437.5 ms | 22.6 ms | 19.33x | 25.6 ms | 39.72x |
| pure read 64 MiB | 263.1 ms | 8.3 ms | 31.54x | 8.5 ms | 30.26x |
| pure copy 64 MiB | 852.9 ms | 21.7 ms | 39.27x | 22.0 ms | 41.47x |
| overwrite 64 MiB | 272.6 ms | 8.3 ms | 32.91x | 8.5 ms | 43.35x |
| git | |||||
| git init + commit 100 files | 459.2 ms | 40.3 ms | 9.56x | 635.4 ms | 0.72x |
| git clone (shallow, ~1MB) | 549.1 ms | 421.0 ms | 1.30x | 576.2 ms | 0.84x |
| npm | |||||
| npm init + tiny install | 598.5 ms | 630.7 ms | 0.95x | 630.7 ms | 0.95x |
Full cloudflare/sandbox-sdk npm install
| Target | Duration |
|---|---|
tmpfs (/tmp) | 34.3 s |
computerd FUSE (/workspace) | 124.7 s |
ext4 disk (/var/tmp) | 63.9 s |
computerd is ~2x slower than the container's ext4 disk for the full
npm install, and ~3.6x slower than tmpfs. The disk comparison is
the more realistic baseline for general usage.
Where computerd is faster than the disk baseline
The in-memory inode store beats real disk on metadata-heavy work:
stat, rm, mkdir tree, find tree, git init, git clone,
npm init. Those eight scenarios cover most of the day-to-day cost
of tools like git status, module resolution, and incremental
builds.
Where computerd is slower
Large sequential file I/O. The computerd write path hashes each
CHUNK_SIZE (512 KiB) chunk
into a content-addressed blob store on every release; that's how
the Durable Object can sync only the chunks that changed and
deduplicate identical content. The cost lands on raw
dd-style throughput numbers but rarely on real developer
workloads, which is why npm init + tiny install matches the disk
baseline despite pure read 64 MiB being 30x slower.
Reproducing
bash script/run-fs-bench.sh
or against a deployed computerd-container instance, upload
script/fs-bench.sh and run it with
MOUNT=/workspace BASE=/tmp.