hesela.devFull-stripe write
A parity-array write supplying replacement data for every data position of a stripe so its new parity can be computed without reading the prior stripe contents.
Parity is still written: a healthy stripe with k equal-size data blocks and p parity blocks writes k+p blocks for k blocks of payload in Hesela's model. Covering the stripe requires the appropriate address alignment and aggregation at the parity layer, not merely a host request of matching length. Linux MD's journal may collect writes before destaging; cache capacity and timing constrain that aggregation.
Relations
- related
- read-modify-write, reconstruct-write, parity-raid, raid-write-hole, write-amplification
Advantages
- Eliminates old-data and old-parity reads for parity computation when all replacement data is present
Limitations
- Does not eliminate parity write traffic, lower-layer overhead or crash-consistency requirements
- Request splitting and misalignment can leave partial stripes
- Early acknowledgement from a write-back journal is a different durability boundary from final member placement