Kioxia Demonstrates RAID Offload Scheme for NVMe Drives

At FMS 2024, Kioxia had a proof-of-concept demonstration of their proposed a brand new RAID offload methodology for enterprise SSDs. The impetus for that is fairly clear: as SSDs get quicker in every era, RAID arrays have a serious drawback of sustaining (and scaling up) efficiency. Even in instances the place the RAID operations are dealt with by a devoted RAID card, a easy write request in, say, a RAID 5 array would contain two reads and two writes to totally different drives. In instances the place there isn’t a {hardware} acceleration, the info from the reads must journey all the best way again to the CPU and important reminiscence for additional processing earlier than the writes may be executed.

Kioxia has proposed using the PCIe direct reminiscence entry characteristic together with the SSD controller’s controller reminiscence buffer (CMB) to keep away from the motion of knowledge as much as the CPU and again. The required parity computation is finished by an accelerator block resident inside the SSD controller.

In Kioxia’s PoC implementation, the DMA engine can entry the complete host handle house (together with the peer SSD’s BAR-mapped CMB), permitting it to obtain and switch knowledge as required from neighboring SSDs on the bus. Kioxia famous that their offload PoC noticed near 50% discount in CPU utilization and upwards of 90% discount in system DRAM utilization in comparison with software program RAID executed on the CPU. The proposed offload scheme can even deal with scrubbing operations with out taking over the host CPU cycles for the parity computation process.

Kioxia has already taken steps to contribute these options to the NVM Specific working group. If accepted, the proposed offload scheme can be a part of a regular that would develop into broadly obtainable throughout a number of SSD distributors.