Remote Infrastructure Management: May 2020

What is NVMe?

NVM Express (NVMe) is a data storage protocol that delivers the fastest response times for business-critical enterprise applications. However, NVMe is more than a storage specification; the broader NVMe over Fabrics protocol encompasses the entire data path, from server to network to storage system.

NVMe—the NVM Express data storage standard—is emerging as a core technology for enterprises that are building new storage infrastructures or upgrading to modern ones.

NVMe is both a protocol optimized for solid-state storage devices, and a set of open-source architectural standards for NVMEM components and systems.

NVMe adds some new names for some common structures.

An NVMe Qualified Name (NQN) identifies an endpoint and is similar to an iSCSI Qualified Name (IQN) in both format (domain registration date, domain registered, and something unique like a serial number). A namespace is analogous to a LUN (Logical Unit Number, a unique identifier for a logical or physical device); both represent an array of blocks presented to an initiator. A subsystem is analogous to an initiator group (igroup) (subsystems have considerably more functionality but for our purposes, we are focusing on how to map LUNs/namespaces), it is used to mask an initiator so that it can see and mount a LUN or namespace. Asymmetric Namespace Access (ANA) is a new protocol feature for monitoring and communicating path states to the host operating system’s Multipath I/O (MPIO) or multipath stack, which uses information communicated through ANA to select and manage multiple paths between the initiator and target.

NVMe will become an essential part of the modern data center, because it addresses three crucial attributes of data storage performance: IOPS, throughput, and latency.

The IOPS and bandwidth improvements are primarily the result of NVMe’s flexibility and its ability to take advantage of fast transport technologies to move NVMe commands and data.

These transports include:

• FCP. Currently available in speeds of 16 and 32Gbps and soon 64Gbps.

• RDMA Protocol.

Data center fast Ethernet: Currently available in 25, 40, 50, and 100Gbps.

InfiniBand: currently available with speeds up to 100Gbps.

• PCI Express 3.0. Supports 8 gigatransfers per second (GT/s), which translates to approximately 6.4Gbps.

NVMe accelerates many of today’s most important emergent business workloads:

Artificial intelligence (AI).

Machine learning (ML)/deep learning (DL).

Internet of Things (IoT).

NVMe as a Storage Attachment Architecture

NVMe is most commonly used today for attaching disks and disk shelves. Many storage vendors and suppliers have introduced offerings based on using NVMe as a storage-attachment architecture and standard. Technically, in most cases, NVMe is the protocol used to perform I/O, whereas the physical transport is primarily PCIe.

In this scenario, NVMe replaces the SCSI command set with the NVMe command set and frequently replaces SATA or serial-attached SCSI (SAS) with PCIe to connect drives to the storage controller. NVMe relies on a physical attachment and transport. It uses PCIe as the transport.

NVMe-attached flash offers more bandwidth and reduced latencies because:

• It offers more and much deeper queues: 64k (65,535) queues, each with a queue depth of 64k.

• The NVMe command set is streamlined and therefore more efficient than legacy SCSI command sets.