With the addition of VSL, the Fusion ioMemory architecture now brings the full disruptive potential of solid state memory to the enterprise.
Fusion's VSL is a flash-based subsystem to accelerate today's enterprise-class operating systems. It virtualizes NAND flash arrays, combining key elements of the two pillars of modern operating systems: the I/O subsystem and the virtual memory subsystem.
VSL combines the advantages of a virtual memory architecture with a transactional file system approach on an array of NAND flash.
The I/O subsystem in today's operating systems includes a common interface for block-based applications, such as file systems, volume managers, and applications, to access persistent data (storage). VSL utilizes this block interface to present ioMemory modules (i.e. ioDrives) to the operating system as easily accessible block-based storage that existing file systems, volume managers, and applications can use just like a conventional disk.
The virtual memory subsystem abstracts logical data addresses from their physical location by creating a directory of data locations. In modern OSs, a 64-bit virtual address space is used to organize and partition data used by the applications and users. Below this virtual address space lays the physical RAM, which has a much smaller address space. Operating systems and applications use this virtual interface to RAM (called the page table) to look up the physical location of data using a directory rather than requiring massive quantities of RAM just to satisfy each application's memory address space.
Similar to page tables in the host virtual memory subsystem, VSL virtualizes Flash via "block tables." VSL translates block requests to physical ioMemory addresses, also analogous to the virtual memory subsystem. It's important to note that these block tables are stored in host memory. This is a key advantage over other solid-state architectures (e.g. SSDs) that store block tables only in embedded RAM, where block tables are accessible only behind legacy storage protocols.
Without VSL, SSDs must serialize access through RAID controllers and use embedded processors to perform block mapping. As data is copied and re-copied through multiple layers of memory and embedded processors, the result is unnecessary context switching, queuing bottlenecks, and I/O storms, which all increase latency.
In addition to seamless integration with the existing software and hardware landscape, VSL also provides a set of enhanced programmatic interfaces. These interfaces pave the way for an entirely new performance-optimized software ecosystem that has already begun to emerge. Examples of this new emerging software ecosystem include,
VSL is the first and only hybrid OS subsystem that bridges the gap between the I/O and virtual memory subsystems. The results are products that combine memory-like performance with the persistence and capacity of traditional storage. Without VSL, NAND flash is destined to remain an expensive niche in a world built around slow disk infrastructure. With VSL and the ioMemory-architecture, innovators can now unlock the true potential of enterprise flash to achieve the highest levels of performance, efficiency, and savings that would otherwise be impossible.
Figure 1. VSL lays the foundation for an emerging ioMemory-optimized software ecosystem that is not possible with legacy I/O subsystems due to obstructions created by the RAID controller and embedded processors.
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