Solid State Drives (SSDs) In, Hard Disk Drives (HDDs) Out!

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SanDisk, in association with Toshiba, has also developed a 256-gigabit 3D NAND chip, with three bits per cell and 48 layers.

Samsung’s three-dimensional vertical-NAND (3D V-NAND) technology has enabled it to make a 6.35cm SSD of around 16TB capacity. V-NAND involves both structural and material innovations. A new technology called the Channel Hole Technology enables the stacked cells to connect vertically through a cylindrical channel that runs through these. This is supplemented with a material innovation called the Charge Trap Flash technology, which prevents data corruption caused by cell-to-cell interference. This technology uses a non-conductive layer of silicon nitride, which wraps around the control gate of a cell, acting as an insulator that temporarily traps electrical charges and maintains cell integrity. While current products and prototypes have 48 layers, Samsung says its technology is capable of 100 layers, which it hopes to achieve by 2017.

In March this year, Samsung officially announced the launch of PM1633a, a 15.36TB drive, for enterprise applications. The SSD is based on a 12-gigabit-per-second serial attached SCSI interface and comes in a 6.35cm form factor.

Keeping up with the networks

The latest networking standards seem to promise nothing short of lightning speed. The emerging Wi-Fi standard 802.11ac operates at 1300Mbps, Wi-Gig (802.11ad) that was introduced in Intel’s sixth-generation Core PC platform can operate at 7000Mbps, universal serial bus (USB) 3.1 at 10,000Mbps and Thunderbolt 3 at 40,000Mbps. Hard disk drives (HDDs) are hopelessly slow in comparison, and that is why no one imagines future personal computers to have these.

SSDs fare much better than HDDs, but even the current-generation serial AT attachment (SATA) SSDs—that typically have speeds of about 4400Mbps—do not seem any match for the latest networks. What is to be noted here is that, the NAND flash memory is not the bottleneck but the SATA interface is. In order to overcome this, the industry has standardised on a protocol called non-volatile memory express (NVMe) that communicates over the PCIe host interface. NVMe is considered to bode well for the SSD industry because this technology has been developed for solid-state storage, which means a lot of parallelism and other exceptional features have been designed into it. Plus, standardisation of this technology will eventually drive down the cost, making SSDs more affordable to everybody.

The NVMe interface scales up by using multiple lanes. For example, an NVMe SSD with four lanes has a speed of 32,000Mbps, which is many times faster than SATA SSDs. While SATA supports a single queue of up to 32 commands, NVMe supports 64,000 queues that can each hold up to 64,000 commands.

Let us say, you have a quad-core computer. NVMe will enable commands to be completed in parallel across all the four cores, while in the case of SATA the commands have to go through a single core. That way, NVMe increases throughput and reduces latency. With an NVMe SSD and a fast network connection, data sharing from your laptop will be super-fast. Experts feel that the speed of NVMe SSDs will also extend a laptop’s battery life. If you take the example of a data transfer job that requires an HDD to operate at an active power of 6W for 180 seconds, an NVMe SSD can complete the same task in 10 seconds. This means 6W of active power for just 10 seconds, after which it reverts to idle power.

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NVMe SDDs will also reduce the footprint and power consumption of large data centres, because on an average 10 SATA SSDs can be replaced with one NVMe SSD.

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