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Don't expect SSDs using PLC until 2026, says WD President

by Mark Tyson on 15 June 2021, 13:11

Tags: WD (NYSE:WDC)

Quick Link: HEXUS.net/qaeqp4

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The management of Western Digital Corporation (WD) recently took part in a Bank of America Merrill Lynch 2021 Global Technology Conference Call. During the call, Wamsi Mohan a senior equity research analyst from the BoA, quizzed both Siva Sivaram (WD President), and Robert Eulau (WD EVP & CFO) about WD's current and future business. One of the more interesting topics touched upon during the call, documented by Seeking Alpha, was talk about SSDs moving to using PLC (Penta-Level Cell, five bits per cell) flash NAND for data storage.

As Computer Base reports, flash partners Kioxia and WD already announced work on PLC back at the Flash Memory Summit 2019. However, it still seems like the technology won't be mainstream for at least half a decade. Behind this decision is the knowledge that to move from QLC to PLC gains just 25 per cent storage per cell and "To get that gain you're sacrificing a lot, you need additional redundancy, additional ECC," noted Sivaram, WD President, "so the net gain opposed to the performance loss may not be quite as desirable".

ComputerBase takes the visual chart from WD and helpfully puts a number on the trailing wiggly line – for its relatively small potential increase in storage, a PLC controller must be able to read/write 32 voltage states per cell. This is a much more complex / exacting task for controllers to do. You can see as the bits per cell increase linearly, the states per cell increases exponentially – which is a technical challenge.

Current QLC technology drives are already looked down upon by enthusiasts, and even those with SLC cache buffers are commonly seen to suffer when that cache is filled/overladen. Remember, as QLC is typically a cost saving option, product designers will have to minimise product caches.

Intel was previously confident that its floating gate PLC NAND would be better suited to the job than rival charge trap technology, but it subsequently sold its NAND division to SK hynix. We don't have any updates on SK hynix PLC developments at this time.



HEXUS Forums :: 14 Comments

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QLC's already in a position where performance drops off a cliff once you exhaust the SLC cache and this will make write endurance and charge retention worse. What's it even for, beyond proving it's possible?
DJNW
QLC's already in a position where performance drops off a cliff once you exhaust the SLC cache and this will make write endurance and charge retention worse. What's it even for, beyond proving it's possible?

Storage density, it's why technology like SMR in Hard Drives were created to increase density within a storage footprint.
When people (tech savvy) are already complaining about QLC drives they decide to come up with something that is objectively even worse….

This really sounds like it's a ‘cheaper to produce’ product rather than one which would actually be ‘good’ for consumers.
DJNW
QLC's already in a position where performance drops off a cliff once you exhaust the SLC cache and this will make write endurance and charge retention worse. What's it even for, beyond proving it's possible?

There are certainly some use cases for QLC drives that we don't see as nerds. Most normie users are never going to exhaust that SLC cache and the endurance issues simply don't matter to them. It's to be expected that demand for capacity will continue to rise and it's possible that the size of drive that needs PLC will become standard. Once one company starts advertising a 5TB SSD in a laptop then everyone else will come along and match it. Most people don't know anything beyond that level of detail and, really, why should they?

I didn't realise how complex designing and building a computer really is until Linus got one of his admin team who doesn't know anything about computers to build one.
philehidiot
There are certainly some use cases for QLC drives that we don't see as nerds. Most normie users are never going to exhaust that SLC cache and the endurance issues simply don't matter to them. It's to be expected that demand for capacity will continue to rise and it's possible that the size of drive that needs PLC will become standard.

True. I was surprised by the size of a full Borderlands 3 install last week. Even non-MMOs are getting chunky. Suppose it has its upsides - pressure on ISPs to raise connection speeds and host a steam cache.