Are SATA SSD's DRAM-less?

[Dub7030]

Are all SATA SSD's DRAM-less or am I missing something. I got two Team Group CX2 2TB a little while ago and I dont know if it could be causing some of weird issues im encountering. Do SATA SSD's even have DRAM? 

[RONOTHAN##]

2 minutes ago, Dub7030 said:

Do SATA SSD's even have DRAM? 

Some do, some don't. The Crucial MX500 does, for instance, while the Crucial BX500 does not. 

 

Not sure about that drive, I'd have to look it up, though most of the TeamGroup SSDs I'm aware of are DRAM-less so it wouldn't surprise me if that one was DRAM-less as well. 

[Dub7030]

Do you know if any of the team group drives have DRAM? If you have other recommendations for other sata SSD's that have DRAM im open for suggestions.

[Naijin]

59 minutes ago, Dub7030 said:

Are all SATA SSD's DRAM-less or am I missing something. I got two Team Group CX2 2TB a little while ago and I dont know if it could be causing some of weird issues im encountering. Do SATA SSD's even have DRAM? 

https://www.teamgroupinc.com/en/product/cx2

DRAM Cache:

NO

 

So yours do not have DRAM. Higher end models (like Samsung EVO) do have DRAM.

[Dub7030]

I dont know how to tell the difference, they dont exactly put it on the spec sheet. How can you tell the difference?

[Naijin]

23 minutes ago, Dub7030 said:

I dont know how to tell the difference, they dont exactly put it on the spec sheet. How can you tell the difference?

You'll notice it when moving lots of files or large files, the data transfer speed will tank after a bit and may sometimes just feel snappier.

[mariushm]

The DRAM memory is not used to cache writes, it's used to keep a copy of the list of files and where each file is stored in the flash memory chips. Without DRAM the controller inside the drive has to use a hidden portion of flash memory to store information about where each file is stored in the memory chips, and writing to flash memory is a bit slower than writing to a dram chip.

With a DRAM chip, the updates to that information are made on the DRAM and periodically these changes are dumped to hidden flash memory for permanent storage (so that at next startup, this data can be loaded into the dram chip, as dram chip loses information without power)

So when you write a lot of stuff and especially when you write multiple things in parallel, a ssd with dram chip will perform a bit better because the controller doesn't have to pause to update the file information table.

 

But the actual write performance when writing sequentially (ex copying a large 10+ GB file) will actually depend on how big of a pseudo-SLC write cache the SSD uses.

All SSDs these days take a bunch of unused flash memory and convert it to a special mode that's much faster to write into, and that allows the SSD to write super fast into this temporary area the file. Later, the ssd controller takes the data and does it to a more permanent location.

So for example, if you have a QLC drive with 100 GB of free space on the drive, the controller could "burrow" 80 GB and convert it to 20 GB of pseudo-SLC write cache memory. When you copy a large 10 GB file, it's written into this 20 GB area at high speeds, like 450 MB or more for a SATA drive, and maybe a minute or so after the file is written there, the ssd controller in the background will slowly copy parts of that 10 GB file into the remaining 20 GB of free disk space that's still in QLC mode.

If you happen to copy a file bigger than 20 GB or however much the pseudo-SLC cache is, as soon as you go over the cache amount, the write speeds will drop to the actual QLC write speeds, which can be in the 40-150 MB/s.

 

Some SSD drives can have as little as 5-10 GB of such write cache, other drives can convert pretty much ALL the free disk space in such mode and gradually convert portions back to TLC or QLC as you fill the drive with data (for example a 2 TB empty QLC drive would have nearly 500 GB of pseudo-slc write cache, so you wouldn't notice speed degradation. As you copy a 10 GB file to such drive, the drive takes 5-10 of pseudo-slc write cache and reverts it back to 20-40 GB of QLC memory and slowly moves that 10 GB file into this area of QLC memory and now you have 490-495 GB of pseudo-SLC cache and 20-40 GB of QLC memory .. and so on.