The Crucial P1 1TB SSD Review: The Other Consumer QLC SSD
by Billy Tallis on November 8, 2018 9:00 AM ESTAnandTech Storage Bench - Heavy
Our Heavy storage benchmark is proportionally more write-heavy than The Destroyer, but much shorter overall. The total writes in the Heavy test aren't enough to fill the drive, so performance never drops down to steady state. This test is far more representative of a power user's day to day usage, and is heavily influenced by the drive's peak performance. The Heavy workload test details can be found here. This test is run twice, once on a freshly erased drive and once after filling the drive with sequential writes.
When the Heavy test is run on an empty drive, the large SLC cache of the Crucial P1 enables it to deliver an average data rate that is competitive with most high-end NVMe SSDs. When the drive is full and the SLC cache's size is greatly reduced, the performance drops to well below that of a typical mainstream SATA SSD. This behavior is essentially the same as that shown by the Intel 660p.
The empty-drive run of the Heavy test doesn't push the latency of the Crucial P1 up any higher than is typical for high-end NVMe drives. Things get more interesting on the full-drive test run, where the average latency from the P1 increases by a factor of 12 and the 99th percentile latency increases by a factor of 58. The average latency from the P1 is only slightly worse than the Intel 660p, but the 99th percentile score is three times that of the 660p.
The average read latency of the Crucial P1 is significantly affected by whether the test is run on a full or empty drive, but even the worse of the two scores is still clearly better than what the Crucial MX500 manages. On the write side of thing, filling the drive has an almost catastrophic effect on latency, driving the average up by a factor of 17, an even more severe impact than the Intel 660p shows.
The 99th percentile read latency from the Crucial P1 is typical for high-end NVMe SSDs for both the full and empty drive test runs. The high overall 99th percentile latency is due entirely to the write portion, where filling the drive increases 99th percentile write latency by almost two orders of magnitude.
The total energy consumption of the Crucial P1 during the Heavy test is significantly higher than for the Intel 660p, and the difference between the empty and full drive test runs is larger for the P1 than for any other drive.
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DanNeely - Thursday, November 8, 2018 - link
When DDR2 went mainstream they stopped making DDR1 dimms. The dimms you could still find for sale a few years later were old ones where you were paying not just the original cost of making them, but the cost of keeping them in a warehouse for several years before you bought them. Individual ram chips continued to be made for a while longer on legacy processes for embedded use but because the same old mature processes were still being used there was no scope for newer tech allowing cost cutting, and lower volumes meant loss of scale savings meaning that the embedded world also had to pay more until they upgraded to new standards.Oxford Guy - Thursday, November 8, 2018 - link
The point was:"QLC may lead to higher TLC prices, if TLC volume goes down and/or gets positioned as a more premium product as manufacturers try to sell us QLC."
Stopping production leads to a volume drop, eh?
romrunning - Thursday, November 8, 2018 - link
"There is a low-end NVMe market segment with numerous options, but they are all struggling under the pressure from more competitively priced high-end NVMe SSDs."I really wish all NVMe drives kept a higher base performance level. QLC should have died on the vine. I get the technical advances, but I prefer tech advances increase performance, not ones that are worse than their predecessor. The price savings, when it's actually there, isn't worth the trade-offs.
Flunk - Thursday, November 8, 2018 - link
In a year or two there are going to be QLC drives faster than today's TLC drives. it just takes time to develop a new technology.Oxford Guy - Thursday, November 8, 2018 - link
Faster to decay, certainly.As I understand it, it's impossible, due to physics, to make QLC faster than TLC, just as it's impossible to make TLC faster than MLC. Just as it's impossible to make MLC faster than SLC.
Workarounds to mask the deficiencies aren't the same thing. The only benefit to going beyond SLC is density, as I understand it.
Billy Tallis - Thursday, November 8, 2018 - link
Other things being equal, MLC is faster than TLC and so on. But NAND flash memory has been evolving in ways other than changing the number of bits stored per cell. Micron's 64L TLC is faster than their 32L MLC, not just denser and cheaper. I don't think their 96L or 128L QLC will end up being faster than 64L TLC, but I do think it will be faster than their 32L or 16nm planar TLC. (There are some ways in which increased layer count can hurt performance, but in general those effects have been offset by other performance increases.)Oxford Guy - Thursday, November 8, 2018 - link
"Other things being equal, MLC is faster than TLC and so on"So, other than density, there is no benefit to going beyond SLC, correct?
Billy Tallis - Thursday, November 8, 2018 - link
Pretty much. If you can afford to pay for SLC and a controller with enough channels and chip enable lines, then you could have a very nice SSD for a very unreasonable price. When you're constrained to a SATA interface there's no reason not to store at least three bits per cell, and even for enterprise NVMe SSDs there are only a few workloads where the higher performance of SLC is cost-effective.Great_Scott - Monday, November 12, 2018 - link
They should drop the SLC emulation and just sell the drive as an SLC drive. Sure, there may be some performance left on the table due to the limits of the NVME interface, but the longevity would be hugely attractive to some users.They'd make more money too, since they could better justify higher costs that way. In fact, with modern Flash they might be able to get much the same benefit from MLC organization and have roughly half the drive space instead of 25%.
Lolimaster - Friday, November 9, 2018 - link
Do not mix better algorithms of the simulated SLC cache and dram with actual "performance", start crushing their simulated cache and the TLC goes to trash.