Hardware

They turn a QLC SSD into an SLC drive, which becomes more reliable and faster

They turn a QLC SSD into an SLC drive, which becomes more reliable and faster

The SSD drive have revolutionized the world of storage, offering superior performance and greater reliability compared to traditional magnetomechanical hard disks. Him too QLC SSD (Quad-Level Cell) more recent ones have proven to be fast and reliable even if on paper they shouldn’t be.

An SLC SSD (Single-Level Cell), in fact, retains only one bit in each memory cell. This means that each cell can exist in one of two charge states: “0” or “1”. The representation of these bits occurs through the voltage variation applied to the cell. A higher voltage value represents a “1” state, while a lower value indicates a “0” state. This simplicity of data representation allows high performance and a major one durationbut it also involves relatively low storage capacity and higher costs.

In the article on how SSDs really work we also explained the approach used in the case of MLC drives (Multi-Level Cell), TLC (Triple-Level Cell) and QLC.

The difference between SLC, MLC, TLC and QLC SSDs, in short

If SLC-type solid-state drives store only one bit per cell, the MLC they conserve due bit of data in each memory cell. The voltage variation is used to represent four different states of charge, thus allowing the memorization of four binary combinations (22).

In the case of TLC devices, they manage three bits of data in each memory cell, bringing the binary combinations to 8 (23). With QLC drives, you go even further with storage four bits of data in each cell. The variation in voltage is used here to represent 16 different states of charge (24), allowing a wide range of binary combinations.

Moving from SLC technology to QLC, the storage capacity therefore data density grows more and more, generally to the detriment of performance and durability.

As the number of charge states increases, it becomes more complex for the controller SSD accurately distinguish between different voltage levels representing various data bits. This can lead to a increase in errors reading and, consequently, a greater probability of data loss or information corruption. To compensate for this problem, SSD controllers must implement more sophisticated algorithms for error correction, but these algorithms also suffer from limitations in terms of performance and effectiveness (especially when talking about QLC units). Do you think that we have been talking about SSD PLC for some time now (Penta-Level Cell) capable of storing up to 25 that is, well 32 values for a single cell.

The features of the Crucial BX500 SATA QLC SSD

The engineer Gabriel Ferraz has just presented an interesting project that aims to show how much is lost in the transition fromsolid state drive SLC to a QLC model in terms of durability and performance. Ferraz’s work is described in detail in this YouTube video.

The technician chose a 512 GB Crucial BX500 QLC SSD as a “sacrificial victim”: it is a SATA III drive that relies on a Silicon Motion SM2259XT2 controller with a 32-bit ARC single-core CPU (speed clock equal to 550 MHz). The unit Crucial BX500 QLC It provides two channels of 800 MT/s and does not use any DRAM cache. Each channel also manages two die of memory NAND flash Micron.

Technical characteristics Crucial BX500 QLC SSD

I due die NAND flashes are designed, by manufacturer specifications, to work at 1.600 MT/s (800 MHz) but, when tested in practice, they are castrated at 525 MT/s within the Crucial marked unit.

L’life expectation Of these dieFurthermore, it is 1,500 P/E cycles for FortisFlash NAND chips; of approximately 900 P/E cycles for Mediagrade chips. The P/E indication refers to trading cycles programming and cancellation (Program/Erasure) that memories can handle before their performance or reliability begins to degrade.

Turning your Crucial QLC drive into an SLC SSD improves performance and durability

Ferraz explains that he got to work to Transform your Crucial SSD from QLC to SLC so as to verify performance and durability. Making the SSD media become a drive pSLC (pseudo-SLC), with the storage of only one bit per cell instead of four, the number of P/E cycles would even increase to 100,000 and 60,000, depending on the chip in use.

The life of the unit also changes to 4000 TBW (in another article we talked about the formula for evaluating the durability of SSDs), a value that represents a leap forward of 3000% compared to that ensured by the Crucial BX500 SSD as released on the market.

The counterpoint is, obviously, the capacity of the drive, which drops from the initial 512 GB to just 114-120 GB.

How did Ferraz perform the “magic”? First, he downloaded the MPtools software for the Silicon Motion SM2259XT2 controller and then looked for reference to the memories actually used in the Crucial SSD. By carefully modifying some configuration parameters, he was able to generate a configuration file supported by the SSD to force it to run in SLC mode rather than the standard QLC approach.

After loading the firmware modified, the engineer was able to ascertain the improvement both in terms of performance and duration guaranteed following the transition to the SLC scheme.

Image credit in the article: Gabriel Ferraz.

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