If block cleaned before client reads it but after metadata fetch, get error and retry metadata fetch. Adding storage servers on the fly - need to keep track of how many storage servers make up a stripe group for some files. Cleaning moves files to larger stripe group over time. If partial fragment, use checksum to detect. After file manager crash, reprocess all deltas after checkpoints.
Version numbers give idempotency, and ordering of deltas across all clients' logs.
Checkpoint stripe cleaner state. At 4 servers, FDDI saturation stops linear scalability. Flaws file manager as centralization point is clearly flawed.