Whole-Drive Fill

This test starts with a freshly-erased drive and fills it with 128kB sequential writes at queue depth 32, recording the write speed for each 1GB segment. This test is not representative of any ordinary client/consumer usage pattern, but it does allow us to observe transitions in the drive's behavior as it fills up. This can allow us to estimate the size of any SLC write cache, and get a sense for how much performance remains on the rare occasions where real-world usage keeps writing data after filling the cache.

The SLC write cache in the 1TB SK hynix Gold P31 runs out after just over 100GB of writes. After the SLC cache fills up, the Gold P31's sequential write performance becomes highly variable, ranging from about 1.4 to 2.3 GB/s with little change in character across the entire TLC filling phase. There are no obvious patterns of periodic garbage collection cycles visible at this scale.

Sustained 128kB Sequential Write (Power Efficiency)
Average Throughput for last 16 GB Overall Average Throughput

Despite the variability, the P31's long-term sustained write performance is excellent. It averages out to the best overall write throughput we've measured from a 1TB TLC drive, and in all that variation the performance never drops down to a disappointing level.

Working Set Size

Most mainstream SSDs have enough DRAM to store the entire mapping table that translates logical block addresses into physical flash memory addresses. DRAMless drives only have small buffers to cache a portion of this mapping information. Some NVMe SSDs support the Host Memory Buffer feature and can borrow a piece of the host system's DRAM for this cache rather needing lots of on-controller memory.

When accessing a logical block whose mapping is not cached, the drive needs to read the mapping from the full table stored on the flash memory before it can read the user data stored at that logical block. This adds extra latency to read operations and in the worst case may double random read latency.

We can see the effects of the size of any mapping buffer by performing random reads from different sized portions of the drive. When performing random reads from a small slice of the drive, we expect the mappings to all fit in the cache, and when performing random reads from the entire drive, we expect mostly cache misses.

When performing this test on mainstream drives with a full-sized DRAM cache, we expect performance to be generally constant regardless of the working set size, or for performance to drop only slightly as the working set size increases.

As expected for a drive with a full size DRAM buffer, the P31's random read latency is unaffected by spatial locality: reading across the whole drive is just as fast as reading from a narrow range. And the only other TLC drives that can match this read latency are the two Toshiba/Kioxia SSDs with 96L BiCS4 TLC NAND, but they can't maintain this performance across the entire test.

SK hynix Gold P31 1TB Review AnandTech Storage Bench
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  • ballsystemlord - Thursday, August 27, 2020 - link

    @Billy Thanks for the review. There have been several new SSD releases this year. I look forward to more SSD articles! Reply
  • ballsystemlord - Thursday, August 27, 2020 - link

    Of course, I'm assuming manufacturers are sampling you guys. (: Reply
  • serendip - Thursday, August 27, 2020 - link

    There needs to be more options for 2230 and 2242 drives. More laptops are coming out with replaceable drives in those smaller form factors. Reply
  • Samus - Friday, August 28, 2020 - link

    Kinda feel stupid for buying an SN750 a few weeks ago... Reply
  • vladx - Friday, August 28, 2020 - link

    Still an excellent drive, a bit pricey though... Reply
  • cfbcfb - Sunday, August 30, 2020 - link

    Just installed one in my desktop t replace an older Hynix OEM 256GB drive.

    Zero issues cloning, I used Macrium to "backup everything needed for windows" to another drive, made a usb stick with standalone macrium, put in the p31 and booted from the usb, restored the image and I was off and running.

    Stunning speed for the price, especially the write speed. In some instances I'm seeing faster writes than reads. And hey, power savings and less heat from a non heatsink nvme drive is okay in a desktop too! That's one of the reasons why I got it. With most other high end drives you need a heatsink unless you have a fan blowing on it, and in my system the m.2 slot is right next to the gpu in the only x16 slot, and the nearest fan is the cpu heatsink fan.

    So my old drive would often hit 60-80c. No bueno. This one? After hammering it, its still barely warmer than ambient case temp. Plus its one sided, which is nice.

    A WD 750 black with heatsink or an 8200 pro with heatsink are MUCH more expensive.

    This is a MSRP deal of the year for nvme high end drives. Durability and warranty are also excellent.

    So its not just for laptops. Don't hesitate to buy this drive if you want a high end nvme SSD in ANY device.
    Reply
  • nfriedly - Monday, August 31, 2020 - link

    Is the Gold P31 a single-sided drive or a double-sided drive? (In other words does it have any components on the bottom?) There are a few smaller laptops, such as the GPD Win Max, that only have room for single-sided drives. Reply
  • Srikzquest - Wednesday, October 14, 2020 - link

    This one is a single sided drive, that's a plus against ADATA's XPG 8200 Pro. Reply
  • AnarchoPrimitiv - Monday, August 31, 2020 - link

    I'll hold back on calling it a "fantastic laptop drive" until it's actually put in a laptop with battery duration tests performed and compared to other drives. If it's power savings only equate to 15 extra minutes of battery in real life for example, then it's definitely not worth the compromise on performances. Reply
  • Srikzquest - Wednesday, October 14, 2020 - link

    That's the point, there is hardly any compromise with performance. Its equally good on Efficiency and Performance. Reply

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