Penta-level cell flash and VAST Data

VAST Data is looking at using penta-level cell (PLC) flash in its all-flash storage systems, with a 25 per cent increase in NAND die capacity over its existing QLC flash, so its cost per GB of capacity can go down.

The company’s Universal Storage pitch includes the idea that its all-QLC (4bits/cell) flash design, combined with deduplication, effectively matches disk drive storage cost but delivers all-flash array speed. As PLC flash has 5 bits per cell, a quarter more than QLC, NAND die capacity increases by that amount while manufacturing cost doesn’t increase much at all

VAST partnered with Intel to use its Optane 3D XPoint drives for metadata storage and SSDs for data. We thought VAST had a fairly close relationship with Rob Crooke’s non-volatile memory business unit inside Intel. When that unit was sold to SK hynix, with Rob Crooke running the resulting Solidigm business for SK hynix, we remembered Intel had been bullish about PLC and asked Solidigm about its PLC thinking.

Greg Matson, VP for strategic planning and marketing, told us PLC development at Solidigm “is going really well. In fact, we’re already demonstrating silicon in the labs, and are working on the best intercept for PLC SSDs and the enterprise side. … We have strong customer interest in that.”

Jeff Denworth.

Asked if companies like VAST were interested, he said “You can imagine that companies like that are extremely interested.”

We then asked VAST co-founder and CMO Jeff Denworth about this and he told B&F “Yes, we’re well aligned with Solidigm [and] we are talking with them about PLC.”

Matson said “I can tell you that we’re very bullish on the technology, and do not see any deviation from our ability to deliver the kind of industry standard JEDEC, standard daily [use] type specs that deviate at all from TLC or QLC.”

Howard Marks, VAST Data’s tech evangelist, said “If you remember when QLC was at the stage PLC is at now (vendors have prototypes, no external samples) the foundries were predicting 500 Write/Erase cycles for QLC, so that’s what we designed our system for. When the QLC actually came to market it was better than predicted (1,000 W/E cycles) which was good for us. Now I hear they’re predicting 2000ish cycles and that sounds pretty good.”

If Solidigm can produce PLC NAND dies that have acceptable speed and endurance characteristics like TLC and QLC NAND, then VAST Data could adopt it for Universal Storage arrays and so inch a step closer to its goal of replacing disk drive storage in filers and object storage.

The VAST Lightspeed NVMe enclosure currently comes with 675TB or 1,350TB of QLC flash. That could change with PLC flash to 843.75TB or 1,687.7TB for the same price, or a small incremental cost. VAST uses 15.36TB or 30.72TB Intel QLC drives and these could become, we speculate, Solidigm 19.2TB or 38.4TB PLC drives, applying a 25 per cent capacity uplift.

VAST Data enclosure.

Were VAST to adopt PLC before Pure Storage uses it in its FlashBlade arrays then VAST could have a price/performance advantage in selling into the fast backup/restore market.

When might a VAST PLC flash box conceivably appear? We suggest in the fourth quarter of this year or first quarter of 2023.