Feed: AnandTech
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Title: Kioxia Demonstrates RAID Offload Scheme for NVMe Drives

Date: Mon, 12 Aug 2024 14:30:00 EDT
Link: https://www.anandtech.com/show/21523/kioxia-d...

At FMS 2024, Kioxia had a proof-of-concept demonstration of their proposed a
new RAID offload methodology for enterprise SSDs. The impetus for this is
quite clear: as SSDs get faster in each generation, RAID arrays have a major
problem of maintaining (and scaling up) performance. Even in cases where the
RAID operations are handled by a dedicated RAID card, a simple write request
in, say, a RAID 5 array would involve two reads and two writes to different
drives. In cases where there is no hardware acceleration, the data from the
reads needs to travel all the way back to the CPU and main memory for further
processing before the writes can be done.

Kioxia has proposed the use of the PCIe direct memory access feature along
with the SSD controller's controller memory buffer (CMB) to avoid the
movement of data up to the CPU and back. The required parity computation is
done by an accelerator block resident within the SSD controller.

In Kioxia's PoC implementation, the DMA engine can access the entire host
address space (including the peer SSD's BAR-mapped CMB), allowing it to
receive and transfer data as required from neighboring SSDs on the bus.
Kioxia noted that their offload PoC saw close to 50% reduction in CPU
utilization and upwards of 90% reduction in system DRAM utilization compared
to software RAID done on the CPU. The proposed offload scheme can also handle
scrubbing operations without taking up the host CPU cycles for the parity
computation task.

Kioxia has already taken steps to contribute these features to the NVM
Express working group. If accepted, the proposed offload scheme will be part
of a standard that could become widely available across multiple SSD vendors.

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