Engineering notes from ZeroFS

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Notes on building a filesystem that lives in S3: the storage engine, the protocols on top of it, and the failure modes we test for.

EngineeringJune 28, 202611 min read

Making POSIX filesystems replicated and highly available

A filesystem on S3 has two single-node weaknesses: a window of acknowledged-but-unflushed writes, and a serving gap while the node is down. ZeroFS closes both with a leader, a standby, writer-epoch fencing, semi-synchronous replication, and an fsync that never reports a durability it cannot prove.

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