The Crucial P1 1TB SSD Review: The Other Consumer QLC SSD
by Billy Tallis on November 8, 2018 9:00 AM ESTAnandTech Storage Bench - Light
Our Light storage test has relatively more sequential accesses and lower queue depths than The Destroyer or the Heavy test, and it's by far the shortest test overall. It's based largely on applications that aren't highly dependent on storage performance, so this is a test more of application launch times and file load times. This test can be seen as the sum of all the little delays in daily usage, but with the idle times trimmed to 25ms it takes less than half an hour to run. Details of the Light test can be found here. As with the ATSB Heavy test, this test is run with the drive both freshly erased and empty, and after filling the drive with sequential writes.
As with the Heavy test, the Crucial P1 handles the Light test as well as most high-end drives when the test is run on an empty drive with plenty of free space in the SLC cache. When the test is run on a full drive, the P1's average data rate drops to just below that of the Crucial MX500 SATA SSD.
When the Light test is run on an empty Crucial P1, the average and 99th percentile latency scores are comparable to high-end NVMe SSDs because the test is operating entirely within the SLC cache. When that cache is shrunk by completely filling the drive, both latency scores are an order of magnitude worse. However, the 99th percentile latency is much better than what we saw from the Intel 660p when full.
The average read latency of the Crucial P1 stays reasonably below that of SATA SSDs even when the test is run on a full drive, but the average write latency ends up several times higher than the MX500 SATA drive. The Intel 660p and DRAMless Toshiba RC100 have similar average write latency when full.
The 99th percentile read and write latency scores tell a similar story to the average latencies, but the weaknesses of the Crucial P1 stand out more clearly. Even with a full drive, read latency on the Light test isn't a problem, but write latency can climb to tens of milliseconds.
Energy usage by the Crucial P1 is reasonably low (by NVMe standards) when the Light test is run on an empty drive. When the test is run on a full drive, the P1 uses substantially more energy than the Intel 660p and instead shows comparable efficiency to most high-performance NVMe SSD.
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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.