MCS, UltraDIMMs and memory IO, the new path ahead – part 1

I was  at Storage Field Day 5 (SFD5) last month and got a chance to talk with SanDisk and Diablo Technologies. It turns out that SanDisk’s UltraDIMM product is based on Diablo Technologies MCS hardware.  So the two of them provided a pretty deep dive into the technology and where they want to go with it. Before we go any deeper the UltraDIMMs will be released to the field by IBM under the eXFlash name.

Diablo Technologies

The team at Diablo have been focusing on the x86 standard memory channel for a while now and lately have been trying out different sorts of technologies to connect as CPU memory. The first Memory Channel Storage (MCS) product converts Memory Channel IO to SATA IO. This allows any SATA device to be attached as memory and enjoy lightening fast, memory access times. Access times are clocked at 7µsec. Most PCIe Flash cards have an access latency at 50µsec or more, so this is 7X faster that PCIe Flash.  They also claim the MCS is capable of 20GB/sec. I know enterprise class storage systems that can’t do that. Also, the MCS utilizes 2 memory channels.

Diablo delivers a chip (that converts MemIO to SATA IO) and software that provides a block IO access to the MCS device. Customers of MCS supply their own SATA flash storage device and presumably package it all together in a DIMM compatible card.

But the main problem is that the whole MCS chip and SATA IO flash device has to fit in the form factor of a DIMM. And cannot draw any more power than a memory device can draw, ~10-15W with its corresponding thermal load.

But this seems plenty for a small flash drive.  The MCS is configured as a 4GB DDR3 DIMM.  There is a requirement to patch the BIOS so that it doesn’t run diagnostic memory tests on the MCS device and their software needs to be loaded to access the device as a block device. I believe they currently support Linux O/S with more O/Ss on the way.

Diablo has looked at other applications for their technology including providing an Memory IO accessed Ethernet NIC was mentioned. But it seems flash storage would be a great first application of their technology.  Not clear to me but SAS would also be something that could be done.

Whatever happens after NAND with the next generation semiconductor storage (see my The end of NAND is near post, it seems to me that accessing it as Memory IO would make an awful lot of sense. makes a lot of sense.  Using MCS as the access channel would seem to be a logical next step.

Part 1 of this story is on Diablo Technologies, Part 2 will be on SanDisk and I am not sure but maybe there will be a Part 3 on IBM eXFlash. So stay tuned.

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