Hammerspace founder and CEO David Flynn has proposed an NFS SSD. Flynn’s notion is based on NFS Ethernet SSDs. The Ethernet SSD concept has been floated before with Kioxia in 2020, for example, putting a Marvell Ethernet controller into an SSD and addressing it as an NVMe device using RoCE. It had previously promoted an Ethernet SSD concept in 2018 as Toshiba Memory.
The Hammerspace CEO says conventional SSDs, when accessed by NFS clients over NVMe, have chatty PCIe connections with up to nine of them per NFS access.
The X device is a PCIe switch.
This can be simplified. The DENTRY (in-memory representation of Directory Entry in Linux) INODE mapping can be carried out by the storage system CPU separate from the client-to-NVMe SSD link chain. This mapping identifies where the data being accessed is located in the target SSD.
The SSD is then accessed by Ethernet and carries out mapping operations to find the file data’s address. Part of the file system now resides in the NFS SSD, which needs software running in its controller processor to achieve. The end result is only three connections between the accessing client and the NVMe SSD. That should lower cost and could improve data access performance and write amplification.
With an array of NFS SSDs you could get parallel access, speeding up IO.
Flynn presented his ideas at the 2023 IEEE Massive Storage Systems and Technology (MSST) conference in SantaClara. Analyst Tom Coughlin wrote about them here.
Bootnote
In November 2021 Kioxia launched EM6 SSDs accessed over RoCE NVMe-over-Fabric links and installed in a 24-slot EBOF — an Ethernet Bunch of Flash box — capable of pumping out 20 million random read IOPS. This provided block access to Ethernet SSDs. The EM6 is a native NVMe SSD fitted with a Marvell 88SN2400 NVMe-oF SSD converter controller that provides dual-port 256Gbit/sec Ethernet access. This product appears to have gone away; we’ve asked Kioxia to confirm this and the company said: “The EM6 is no longer available and it was never released to production.”
