Snapshot Generation: Forest vs Lotus
Forest plays an important role in timely, efficient network snapshot generation. Lotus can generate a snapshot too, but doing so is significantly slower and more expensive. On a regular machine, Forest completes a basic chain snapshot export much faster than Lotus and with a fraction of the memory.
Both implementations produce compatible snapshots and can consume snapshots produced by the other.
Lotus snapshots are not compressed by default, whereas Forest compresses them as part of the export. Both implementations can consume compressed snapshots. Compressing a Lotus snapshot after generation is possible, but it adds further to the total time.
Forest snapshots (.forest.car.zst) also embed an index that lets Forest use the file directly as a read-only blockstore, serving blocks in place without importing them into a database. The index is stored in skippable frames, so Lotus and other tools can still read the snapshot; they just ignore the index. Reading a snapshot in place this way is currently Forest-only.