Speed Up Storage and Access with Solid-State Arrays

By Deepshikha Shukla

2299
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There are several types of solid-state storage devices, from small enough to fit in your pocket to all-flash arrays within data centres that can run entire enterprises.

Array-based solid-state drives (SSDs) are manufactured in a variety of lengths (form factors) that can be installed in any storage device. A solid-state array (SSA) is a dedicated all flash storage array. It has its own proprietary data management application and operating system (OS). Samsung 970 Pro NVMe M.2 SSD is among the fastest consumer SSDs. It provides sequential write and read speeds of up to 2700Mbps and up to 3500Mbps, respectively. Samsung V-NAND has a 2-bit MLC flash memory.

Samsung 970 Pro and 970 Evo
Fig. 1: Samsung 970 Pro and 970 Evo (Credit: https://wccftech.com)

NVMe protocol will surely improve in the future. Hence, for best speeds, PCIe-based SSDs are the top choice. Intel Optane memory offers an extremely fast SSD. If you put a card in a four-lane slot, you get four times the bandwidth, at nearly 4Gbps. This makes it fast as compared to a Serial Advanced Technology Attachment (SATA)-based SSD. NVMe is a replacement for AHCI protocol, used in most SATA-based SSDs today.

Common interfaces

The most common SSA interfaces are SATA, Serial Attached SCSI (SAS), Fibre Channel (FC) and Peripheral Component Interconnect (PCI). These are available in various form factors, including 4.6cm (1.8-inch), 6.3cm (2.5-inch) and 8.9cm (3.5-inch).

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SATA interface provides different data throughputs from 1Gbps to 6Gbps, based on the version. PCI Express and SATA interfaces are widely used in most SSDs.

PCI Express interface uses point-to-point architecture to provide high-speed serial expansion card formats, which is the same for graphic cards. PCI-based SSDs provide both data and power connections when plugged into the motherboard. These allow more bandwidth through multiple lanes and faster signaling. PCI is more efficient and, thus, results in high latency because of direct connection to peripherals.

Automated storage approach

The random access time for an SSD storage array is about 0.1ms as compared to 5ms – 10ms for a hard disk drive (HDD). Automated storage tiering approach decides where to move data based on input or output activities. It does not prioritise based on individual application. This allows the SSD array to provide improved data access. To provide enhanced performance, the SSA employs the SSD to store data in block forms. An SSD array can be accessed through multiple physical hosts, so is easy to set up.

A rich software layer governs the SSD arrays and controls a range of activities like compression, replication and snapshots. The type of software determines the functionalities of SSAs. Software is controlled by storage controllers to control data storage. SSAs have a range of advantages such as easy to set up, low latency and storage efficiency. These are also easy to integrate with data centres and solutions.

NAND is a non-volatile flash memory used in SSDs. It can retain data even after the power is turned off. Single-level cells (SLCs), multi-level cells (MLCs) and triple-level cells (TLCs) are the three different types of NAND.

SLCs have faster write speeds, higher program and erase cycles, lower power consumption but are the most expensive. These offer multiple solutions for enterprise use.

MLCs have low write speeds, higher data density, low cost, and low program and erase cycles. These are used for consumer-grade applications.

TLCs have low write speeds, low program and erase cycles, and high storage density. These are also for consumer-grade solutions, and are the cheapest.

Vikas Jain, team leader – electrical schematics and apparatus, Cyient, says, “The technology we are using for SSA devices is NAND flash (SLC, MLC or TLC). Our primary focus is on endurance, safety of data from EMI/EMC interference, magnetic field, data security and good to work in harsh regions like locomotive/railway engines or metro trains. We use Ethernet, RS485, CAN, MVB, I2C and USB for firmware porting/data backup.”

Gartner Magic Quadrant for SSAs

IT and development and operation companies make the best SSAs in the world, as ranked by Gartner Magic Quadrant visionaries. Tintri VMstore T5000 series was among the top-named SSAs by Gartner.

Gartner Magic Quadrant for SSAs 2017
Fig. 2: Gartner Magic Quadrant for SSAs 2017 (Source: Gartner, July 2017)

SSA Magic Quadrant is essentially an all-flash array. It has some unique requirements for an array to qualify into the solid-state chart. It is for SSAs that are on the edge of performance that focus on revenue-generating applications. Most products listed on the solid-state chart are from vendors who claim that the listed arrays are acceptable replacements for hard-disk-based systems.

It is expected that within the next 12 months, SSAs will improve in performance by a factor of 10, and double in density and cost-effectiveness, therefore changing the dynamics of the storage market.

Strategic planning assumption says that by 2021, 50 per cent data centres will use SSAs for high-performance computing and Big Data workloads. These systems include a data management software and an OS optimised for solid-state technology.

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