Fusion-io CEO David Flynn said VSL does for I/O memory what the virtual machine (VM) subsystem does for DRAM. VSL uses direct memory access and low-level physical addressing to talk to I/O memory, and it acts like a native memory module. "It's so fast, it's better than using true RAM," Flynn said.
The internal implementation for the VSL is similar to an OS virtual memory subsystem. The VM keeps page tables and mappings in host memory. Each processor looks up that page table on the fly as it accesses memory. It doesn't defer to an embedded processor on a memory module. Each core does its own address translation. Like the virtual memory subsystem, ioMemory VSL translates block requests to physical ioMemory addresses.
Flynn said the VSL removes Flash's performance limitation of latency created by the multiple hops between a CPU and an SSD resource. "With Flash, you have to have a level of indirection," he said. "Somebody has to map it. Everybody else is trapping that mapping function inside a tiny CPU on the SSD module behind a RAID controller and a storage bus, making it extremely difficult to leverage that level of indirection to offload higher-order functions.
"Making the mapping present and visible within the OS will speed it up just like memory mapping for virtual memory subsystems," Flynn added, "and it lets you leverage this newly presented virtualized address space and resource."
Henry Baltazar, a senior analyst at The 451 Group, sees the ioMemory VSL not as a technology breakthrough, but more of a way for Fusion-io to reposition the company's technology away from the PCIe bus and down to the driver level. Other vendors such as LSI Corp. (using Seagate Technology SSD modules) recently released technology similar to Fusion-io, so Fusion-io has to differentiate itself from the encroaching competition.
Fusion-io was early out of the gate with its PCIe card, and forged partnerships with server vendors Dell inc., Hewlett-Packard Co. and IBM.
"The message that resonates for them and the message that gets them their OEM [agreements] is 'don't buy storage, buy flash cards; make your servers faster,'" Baltazar said. "By taking a step back even further and peeking under the covers of the software layers and virtual storage layer, they're saying they're making it more memory-like. That appeals directly to the server guys that they want to sell to. It's really an amplification of the messaging they're trying to get to these guys."
Fusion-io's Flynn said VSL will significantly improve his company's current and future products. "This new generation of software stack, even under the most demanding conditions can get [up to] five times the performance of the prior generation [in saturated-writes and free-space recovery scenarios]," he said. "Even under standard conditions, it basically doubles our write IOPS. It's capable of doing 120,000 to 140,000 write IOPS."
ioMemory VSL is backwards compatible with Fusion-io's other products, and the firmware upgrade is free to existing customers. Flynn said VSL will also be included in the company's expected 33x nanometer product that's currently shipping to select customers in limited quantities. The general availability for the 33x nanometer product hasn't been announced.