Storing a new file through CDC dedup issued sync_all + a parent-dir
fsync for every ~256 KB chunk (~8,200 fsyncs for a 1 GB upload), plus
one PG INSERT round-trip per chunk. The actual durability boundary is
the manifest INSERT: chunks only need to be durable before any PG row
references them, not one by one.
- BlobStorageBackend grows put_blob_from_bytes_unsynced + sync_blobs
with conservative defaults (unsynced delegates to the synced write,
sync_blobs is a no-op) so backends that don't opt in keep the
per-write durability semantics. Remote stores are durable on PUT.
- LocalBlobBackend writes chunks without fsync and implements
sync_blobs as a parallel sweep: every listed blob file (hard
requirement) plus each distinct prefix directory exactly once
(best-effort, same tier as fsync_parent_dir).
- DedupService::store_chunks writes new chunks unsynced, runs one
sync_blobs sweep, then registers all new chunks in ONE batched
UNNEST INSERT - durability before visibility, and the per-chunk PG
round-trips collapse into one.
- Encrypted/Migration decorators forward both methods so the
optimization survives encrypted-local and live-migration stacks.
https://claude.ai/code/session_013Bk4BMQEvR9QxCU7QXLRwv
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