Optimize snapshot unpack by using multiple accounts directories - #245
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palmerlao wants to merge 4 commits into
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Optimize snapshot unpack by using multiple accounts directories#245palmerlao wants to merge 4 commits into
palmerlao wants to merge 4 commits into
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Unpack coalesces the snapshot's append-vecs into one big file per disk shard, written by an async per-shard writer fed from a pooled tar reader. The full and incremental snapshots share a shard's "data" file (offsets carry across the two sequential phases); a fileId encodes shard = id % N and segment = id / N, with segment 0 the coalesced file and segment >= 2 runtime per-file append-vecs. Records go to the least-backlogged shard by in-flight (queued) bytes, steering toward the fastest-draining disk so throughput approaches the disks' weighted sum; when no disk has a backlog it falls back to an even byte split.
Sort each shard buffer in place. The stages overlap so the disk keeps working while the CPU sorts, instead of each shard reading, sorting, and writing serially.
Tunes how many shard buffers are sorted at once during the flush.
Ingests the flushed SSTs and asserts one entry per key at its highest slot.
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This change speeds up snapshot unpacking by
On my test machine I find that
devtakes15m23sto unpack a snapshot while70f801fcan unpack the same snapshot in6m53s.