NVMe

The industry shift to the NVMe standard has started. More and more vendors are bringing products which are stamped NVMe.

NVM Express (or NVMe) stands for Non-Volatile Memory. NVMe has larger queue depth than SCSI (64000 over 254 for SAS, or 31 for SATA). NVMe Host Controller Interface Specification (NVMHCI), is a specification for accessing solid-state drives (SSDs) attached through the PCI Express (PCIe) bus. NVMe standard will allow up to six times faster data transfer speed than 6 Gbps SAS/SATA SSDs.

NVMe Benefits and advantages
While NVMe is new as technology, it’s just a question of a time when this standard will become a mainstream. Here is a quote from the release notes documents.

I/O requests in an enterprise ecosystem spend much of their time in the hardware infrastructure (that includes NAND flash media, the flash controller, the host bus adapter, related hardware, etc.), and only a small portion of time working through the software I/O stack. The NVMe standard streamlines the software I/O stack by reducing unnecessary legacy overhead and supporting multiple queues, and many more commands per queue than any other commonly used storage protocol.

NVMe supports 64,000 commands per queue (as well as 64,000 queues) to enable extremely fast hardware responses especially when compared to the SAS protocol that can only support 254 commands per queue or the SATA protocol that supports 31 commands per queue.

NVMe Vs AHCI
The AHCI (Advanced Host Controller Interface) command protocol was designed for much slower media (e.g., spinning magnetic disks). AHCI ends up being inefficient with modern SSDs, so a new standard was developed: NVMHCI (Non-Volatile Memory Host Controller Interface). Combine NVMHCI with a fast PCIe interface and you have NVMe, Non-Volatile Memory Express. It’s a much improved interface developed around the needs of flash memory rather than spinning disks.

All applications are latency-sensitive to some extent, but some applications require the utmost performance - a few milliseconds of excess latency in the storage layer can result in seconds of delay at the application level. Enterprise SSDs weigh in to provide the best mix of cost, capacity and performance for the most latency-sensitive applications, but inconsistent performance is the hidden killer of application performance.

Some of the Major Feature of PCIe SSDs are:
Scalable performance;
Better power management;
Lower latency data transfers;
Lower overhead;
Advanced Error Reporting (AER);
Maximized interconnect efficiency;
Native hot plug capability;
High-bandwidth, low pin count implementations;
Hardware I/O virtualization;
Software compatibility with existing PCI.

PCI Express or Peripheral Component Interconnect Express (PCIe) is a relatively new, high-speed serial bus. It is a standards-based, bidirectional, point-to-point serial interconnect that's capable of data transfers of up to 32GB/s. The current PCIe standard is PCI 3.0. PCIe-based devices, like all other forms of SSDs, have no moving parts and can support consumer-based or enterprise-class NAND flash media. You can use PCIe SSDs as storage cache or as primary storage devices.

---