differential-raid · research · also Diff-RAID

Differential RAID

Differential RAID is a research design that combines uneven parity placement with parity reassignment during replacement to maintain different SSD wear ages.

Related Observatory article: Differential RAID on hesela.com

The EuroSys 2010 design targets wear-driven reliability under its model; merely using a dedicated parity drive is insufficient. Full-row writes weaken the intended write imbalance [1].

For a worked calculation, distinguish parity share, member writes, NAND erasures and device failure risk. Host-data volume, not the fraction of requests, weights mixtures of small and full-row writes [2].

Relations

related

RAID 5, Full-stripe write, Read-modify-write, Wear leveling, Write amplification

Advantages

• Makes the relationship between redundancy placement and per-member write load explicit

Limitations

• Write-count differences do not establish a present-day reliability improvement
• Parity reassignment adds replacement work

Citations

1. Balakrishnan et al. Differential RAID: Rethinking RAID for SSD Reliability. EuroSys 2010, sections 3-4. (accessed 2026-10-20)
2. Hesela: parity placement and per-member writes (accessed 2026-10-20)

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