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Micron is all set to be first to market with quad-level cell (QLC) flash drives. Its 5210 QLC Enterprise SATA SSD product will take aim at a niche market of data currently kept on spinning disk in the datacentre, but which requires high-performance read characteristics.
Key use cases targeted will be analytics and content delivery, in particular at cloud and web-scale operations.
Micron’s senior partner management manager, Nicolas Maigne, said the company aimed to push flash to corners of the datacentre it hadn’t gone to before.
“The majority of data in datacentres – around 75% – is still on 7,200rpm spinning disk products, such as helium drives, 10TB and above. The 5210 won’t replace those kinds of drives overnight, but will challenge the high-end portion of the market,” he said.
“The use cases in mind are the performance-sensitive ones, where currently HDDs are aggregated in Raid sets to gain the IOPS required.”
Here, Maigne is referring to short-stroking, where data is striped across large numbers of spinning disk HDDs so it can be read simultaneously from many drives to provide high input/output (I/O) performance.
It is an approach that is wasteful of disk capacity, to which the Micron QLC drive aims to offer an alternative. As well as offering better utilisation, the 5210 also claims a three times better energy usage over spinning disk.
The Micron 5210 is aimed at very read-centric workloads. That’s because QLC – although able to pack more data into a smaller area than existing flash generations – is also more sensitive to wear upon writes.
QLC – as the name suggests – can write four bits per cell.
Compared to single level cell (SLC) drives, which could switch between 0 and 1, and multi-level cell (MLC) drives, which can be switched between four binary states, QLC provides for up to 16 different states via 15 different voltage levels.
To pack all this into silicon literally eats away at the ability to write and rewrite data, in that wear is far more prevalent than with SLC, MLC and even TLC flash.
Micron would not give performance figures for the 5210 QLC – which comes in capacities of 1.92TB, 3.84TB and 7.68TB – but provided ratios compared to its 5200 TLC Eco drives.
So, for example, sequential reads – ie, throughput – will be the same (540Mbps stated for the 1.92TB 5200 TLC Eco SSD), while random reads will come in at 0.8x to 1x (of 95,000 IOPS).
And while sequential write performance for the 5210 QLC drive will be 0.6x to 0.8x (of 520MBps) its TLC stable-mate, for random writes that figure is a lowly 0.25x (of 22,000 IOPS).
Perhaps the most startling difference is in endurance. While the 1.92TB TLC 5200 Eco has stated endurance of 3.5PB in terms of terabytes written (TBW) – ie the expected lifetime volume of data writes it can take – the 5210 QLC will provide a mere 0.05x or 0.1x of that. That’s an expected TBW of 175TB to 350TB.
The 5210 QLC has already started shipping to a “narrow set of partners”, said Maigne, with general availability planned for October 2018.
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