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Does anyone know the write page¹ size of a Western Digital Blue SATA SSD (model numbers WDS200T2B0A or WDS200T2B0B)?

I contacted WD support and they're claiming it is 512B, but most information I've seen on modern SSD's suggests that that is highly unlikely. (That is, while the drive controller can emulate writing to individual 512B sectors, the hardware can't actually write to less than a page, which is likely 4KiB or more.)

Related questions:

...of course I'm asking about a different device, so those aren't duplicates.

(¹ A "page" is the smallest block of data that can be written in a single write operation.)

Edit:

The official answer from Western Digital: "I am sorry but the information that you are looking for is a proprietary information and it is not available for the customers."

According to one source, the NAND chips should be "SanDisk BiCS FLASH 64-Layer TLC", but I can't find any specs on those either... and, of course, WD has one of those "warranty void if removed" stickers hiding the chips so you can't get numbers off of them.

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  • Manual here: wd.com/content/dam/wdc/website/downloadable_assets/eng/…
    – Hashim Aziz
    Commented May 27, 2019 at 20:53
  • ...and did you actually look at that? If it mentions the write page size anywhere, I sure haven't found it. (Am I missing something?)
    – Matthew
    Commented May 28, 2019 at 15:19
  • I couldn't find it either on a skim but I figured I'd link it anyway in case you could.
    – Hashim Aziz
    Commented May 28, 2019 at 15:22
  • Nope. If I could find it documented anywhere (or if WD tech would just tell me), I wouldn't need to ask here 😢.
    – Matthew
    Commented May 28, 2019 at 15:24

2 Answers 2

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(¹ A "page" is the smallest block of data that can be written in a single write operation.)

Going by this definition, there are multiple different "page sizes" which are relevant in a modern SSD:

  1. The minimum size of a write to the raw flash memory. This may be as small as a single bit -- but bits can only be individually programmed (set to 0), not erased (set to 1).

  2. The size of an erase block in the raw flash memory. This is considerably larger; in modern flash devices, it's often multiple megabytes. Notably, this is usually not power of 2, as it includes extra bits for error correction.

  3. The size of an error correction block as implemented by the flash translation layer. I don't know offhand how large these are -- they're probably somewhere between the block size of the translation layer and an entire erase block.

  4. The block size as implemented by the flash translation layer. This is usually either 512 or 4096 bytes for compatibility with common operating systems.

The last of these is the only size which is likely to be relevant to you as an end-user, and you've already been told that it's 512B.

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  • Uh... no. Every other source I've seen agrees that 512 bytes is too small and will cause excessive write amplification. Moreover, I would argue that your (1) is a) what I'm looking for, and b) definitely at least 4KiB according to... basically everyone. Including, of note, en.wikipedia.org/wiki/Flash_memory#NAND_memories (the numbers there seem to be out of date, though, or for very small capacity devices). Also, (4) is useless information, at least as far as performance and endurance.
    – Matthew
    Commented Jun 3, 2019 at 15:23
  • Note (from the linked article): "programming is performed on a page basis". Go read up on modern SSD's... oh, just about anywhere. Maybe read unix.stackexchange.com/questions/334804 while you're at it. Literally every source I've seen agrees that a) the device can only program ("write") in page-sized increments, and b) pages are at least 4KiB, more likely 8KiB or larger on modern, high-capacity devices.
    – Matthew
    Commented Jun 3, 2019 at 15:28
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One can find the papers published by the manufacturers according to you SSD's NAND type, for examples:

  • Samsung QLC (16KB):
    • Kim, Doo-Hyun, et al. "13.1 A 1Tb 4b/cell NAND Flash Memory with t PROG= 2ms, tR= 110µs and 1.2 Gb/s High-Speed IO Rate." 2020 IEEE International Solid-State Circuits Conference-(ISSCC). IEEE, 2020.
  • Samsung TLC (16KB):
    • Kim, Chulbum, et al. "A 512-gb 3-b/cell 64-stacked wl 3-d-nand flash memory." IEEE Journal of Solid-State Circuits 53.1 (2017): 124-133.
  • Intel QLC (16KB):
    • Khakifirooz, Ali, et al. "30.2 A 1Tb 4b/Cell 144-Tier Floating-Gate 3D-NAND Flash Memory with 40MB/s Program Throughput and 13.8 Gb/mm 2 Bit Density." 2021 IEEE International Solid-State Circuits Conference (ISSCC). Vol. 64. IEEE, 2021.

Or maybe do some testing like this question can help. I have tested my WD SN850 and find the page size is 32KB:

enter image description here

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