Storage industry takes steps to avoid PCIe SSD fragmentation
Task force aims at interoperability rules
By Lucas Mearian | Computerworld US | Published: 10:23, 02 April 2012
Fifty industry representatives have signed on to a task force created to address interoperability issues related to a plethora of form factors and connectivity issues for PCIe solid-state drives (SSDs).
The Solid State Storage Initiative (SSSI) PCIe SSD Task Force, which is being organised under the Storage Networking Industry Association (SNIA), will deal with current standards, any standards gaps that need to be filled and end user concerns over interoperability between products.
Solid-state storage devices come in so many shapes and sizes that the electrical signal standards and OS drivers can vary from manufacturer to manufacturer. Unlike SAS and SATA interconnects, which only increase in speed with each new generation of product, PCIe is a good fit for SSDs, as it allows the interface speed to be increased quickly by adding PCIe lanes, according to Paul Wassenberg, chair of SNIA's SSSI.
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But not every SSD or systems manufacturer is speaking the same language when it comes to PCIe, Wassenberg said.
For example, standard SAS and SATA drives plug into a south gate on an Intel motherboard. If you plug that gate into a PCIe bus, it doesn't automatically show up as a mass storage drive on the computer system. A software driver is required for the operating system to recognise the PCIe SSD as a mass storage device, according to Eden Kim, chair of SNIA's Solid State Storage Initiative's technical group.
In addition, in array environments where multiple drives are used for higher capacity and data resiliency, PCIe SSDs do not act the same way as SAS or SATA drives. For example, they cannot be swapped out without disrupting the system. And, in consumer computers, laptops and desktops, there is no easy way to gain access to PCIe cards, Kim said.
"That's a motherboard layout issue," Kim said. "So now you can have a cable coming from your card in the PCI slot on the motherboard to your drive bay that allows you to plug in a PCIe 2.5-in form factor SSD. That's the Micron product."
Currently, the SSSI recognises three categories of PCIe devices: low-end SSDs for tablets, laptops and desktops that may use one or two PCIe lanes, small PCIe cards that use four lanes and full-height cards that use eight lanes.
"This is about getting the nomenclature set so that people can talk and don't have a Tower of Babel," Kim said. "It's more about organising what's out there into cognitive blocks, and providing guidance to the SSD marketplace on PCIe SSDs. This can take the form of educational materials, best practices documents and SNIA standards."
For example, there are already a number of standards groups focused on SSD electrical signalling, including NVMHCI, SATA Express and the Proposed PCI class code assignment for SOP.
The task force will hold its first meeting April 9 and meet on a bi-weekly basis after that. It is structured as an open industry forum for the first 90 days, and thereafter as a SSSI committee. No NDA is required and thus no confidential information is expected to be shared among task force members.