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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DigitalFreak - Thursday, November 8, 2018 - link
At this rate, by the time they get to H(ex)LC you'll only be able to write 1GB per day to your drive or risk having it fail.PeachNCream - Thursday, November 8, 2018 - link
Please don't give them any ideas! The last thing we need is NAND that generously handles a few dozen P/E cycles before dying. We've already gone from millions of P/E cycles to a few hundred in the last 15 years and data retention has dropped from over a decade to under six months. Sure you can get a lot more capacity for the price, but NAND needs to be replaced with something more durable sooner rather than later. (And no, I'm not advocating for Optane either, just something that lasts longer and has room for density improvements - don't care what that something is.)MrCommunistGen - Thursday, November 8, 2018 - link
I was expecting the extra DRAM to provide a more meaningful advantage over the Intel 660p... I guess it makes sense that Intel left it off to save on BOM.Ratman6161 - Thursday, November 8, 2018 - link
This could be a very good standard desktop drive if 1) the price is right and 2) you can accept that the 1 TB drive is really only good for up to 900 GB. You would just partition the drive such that there is 100 GB free (or make sure you always just keep that much space free) so you always have the maximum SLC cach available. For the price to be right, it has to be lower. Taking the prices from the article, the 1 TB P1 is only $8 cheaper than a 970 EVO. Now if they could get the price down to the same territory as the current MX 500 they might have something.Billy Tallis - Thursday, November 8, 2018 - link
Leaving 10% of the drive unpartitioned won't be enough to get the maximum size SLC cache, because 1GB of SLC cache requires 4GB of QLC to be used as SLC. However, 10% manual overprovisioning would definitely reduce the already small chances of overflowing the SLC cache.mczak - Thursday, November 8, 2018 - link
On that note, wouldn't it actually make sense to use a MLC cache instead of a SLC cache for these SSDs using QLC flash (and by MLC of course I mean using 2 bits per cell)? I'd assume you should still be able to get very decent write speeds with that, and it would effectively only need half as much flash for the same cache size.Billy Tallis - Thursday, November 8, 2018 - link
Cache size isn't really a big enough problem for a 2bpc MLC write cache to be worthwhile. Using SLC for the write cache has several advantages: highest performance/lowest latency, single-pass reads and writes (important for Crucial's power loss immunity features), and your SLC cache can use flash blocks that are too worn out to still reliably store multiple bits per cell. A slower write cache with twice the capacity would only make sense if consumer workloads regularly overflowed the existing write cache. Almost all of the instances where our benchmarks overflow SLC caches are a consequence of our tests giving the drive less idle time than real-world usage, rather than being tests representing use cases where the cache would be expected to overflow even in the real world.idri - Thursday, November 8, 2018 - link
Why don't you guys include the Samsung 970 PRO 1TB in your charts for comparison? It's one of the most sought after SSDs on the market for HEDT systems and for sure it would be useful to have your tests results for this one too. Thanks.Billy Tallis - Thursday, November 8, 2018 - link
A.) Samsung didn't send me a 970 PRO. B.) The 970 PRO is pretty far outside the range of what could be considered competition for an entry-level NVMe SSD. It's a drive you buy for bragging rights, not for real-world performance benefits. The Optane SSD is in that same category, and I don't think the graphs for this kind of review need to be cluttered up with too many of those.PeachNCream - Thursday, November 8, 2018 - link
Not to be obtuse, but by price the 970 PRO is well within the range of competition for the P1 given that the 1TB 970 retails for $228 on Amazon right now and the MSRP for the 1TB P1 $220. Buyers looking for a product will most certainly consider the $8 difference and factor that into their decision to move up from an entry-level product to a "bragging rights" option given the insignificant difference in cost. Your first point is valid. I would have stopped there since its reasonable to say, "Physically impossible, don't have one there pal."