When RAID 5 is configured for the new-gen OceanStor hybrid storage, how many write penalties...

In Huawei OceanStor storage systems utilizing RAID 2.0+ and the SmartMatrix architecture, the "write penalty" associated with traditional RAID is mitigated through Full-Stripe Writes. In a partial write (where only some data in a stripe is updated), a RAID 5 setup usually suffers a write penalty of 4 (Reading old data, reading old parity, writing new data, writing new parity).

However, Huawei's controllers utilize a large cache to aggregate incoming data. When enough data is collected to fill an entire stripe (e.g., 8 data chunks plus 1 parity chunk in an 8+1 RAID 5 setup), the system performs aFull-Stripe Write. In this scenario, the system calculates the parity in the CPU/cache and writes the entire stripe to the disks at once. Since no old data or old parity needs to be read from the physical disks before writing, the disk-levelwrite penalty is 0. This significantly enhances the write performance of hybrid arrays, especially those using mechanical HDDs which are highly sensitive to the latency of extra read/write operations.