speculative-partial-write · research · also PARIX

Speculative partial write

A speculative partial write in PARIX logs a replacement value and requests the original only when the parity journal lacks the required baseline.

Related Observatory article: Speculative partial write on hesela.com

The retained baseline applies within a journal epoch, not forever. PARIX is a research prototype, not a Linux MD mode. Its published IOPS comparison excludes background log flushing.

Relations

related

Parity logging, Read-modify-write, Partial Parity Log

Advantages

• Repeated overwrites within an epoch can avoid old-data reads

Limitations

• Replay resets the baseline
• The first write can require an additional exchange and original-value log record

Citations

1. Li et al. PARIX: Speculative Partial Writes in Erasure-Coded Systems. USENIX ATC 2017, sections 3-5. (accessed 2026-10-19)
2. Hesela: RAID write accounting and parity replay traces (accessed 2026-10-19)

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