Will there be a significant performance difference with dramless and dram SSDs.

[Poraf]

I'm planning to get a new SSD, and I've been looking around and reading some reviews and a lot of times I encounter dramless SSDs, and I've heard a while back to avoid dramless SSDs. But some of them actually have positive reviews (something about HMB/SLC? I don't understand much of these yet), I wanted to try them since some were quite cheaper. My use case, aside from games, will mostly be with illustration and graphics and very occasional video editing.

 

If it matters the particular SSDs I was looking at were: WD Blue SN570, Teamgroup MP33, Samsung 980 Nvme.

[TrigrH]

Your main OS drive is better to be on a DRAM ssd. Storing games would be fine on a dramless SSD. Video editing likes fast ssds.

[LAwLz]

It entirely depend on your use case.

The difference between an SSD with and without DRAM will be that the drive with DRAM will do burst writes much faster than the DRAMless. But since most people don't need extremely fast burst writes on their drives, I'd say that it doesn't matter for most people. And as you mentioned, DRAMless drives can use SLC caches and HMB to help with these bursts.

 

If you want a comprehensive comparison between the drives, you need to look at more than just "does it have DRAM or not". There are way more things that goes into an SSD than just DRAM, and all of them matters for performance.

 

I don't know about the Teamgroup MP33, but the WD SN570 and Samsung 980 are very similar performance wise, with the WD Blue probably being slightly better. I don't think we know for sure since I can't find good reviews for the SN570, but the SN550 (before it was downgraded) was slightly better than the Samsung 980, so the 570 with its upgraded flash should be even better.

 

If all of them cost the same, then I'd go for the SN570 out of those three. The problem DRAMless drives have had historically is that they weren't that much cheaper than the better drives. For example the Samsung 980 wasn't that much cheaper than the 970 EVO, and yet the EVO performed quite a bit better.

 

I recommend you check out some reviews where they compare the drives you are interested in vs some other drives around the same price point, for example the Samsung 970 EVO (plus).

 

I don't know what prices are like where you live, but here in Sweden the Samsung 970 EVO Plus 1TB costs the same as the Samsung 980 1TB, and the EVO performs way better in the tests that matters.

[mariushm]

A dramless SSD will be perfectly fine for your usage. 

 

Pretty much ALL SSDs will use a portion of their memory in pseudo-SLC mode, which makes that portion of memory very fast and also has close to SLC levels endurance. 

So you get very fast write speeds until that SLC cache is filled and then speeds slow down until the drive has a chance to empty the SLC write cache again (minutes after you're done writing, the SSD starts moving data from SLC cache into "long term" slower TLC/QLC memory.

 

HMB - host memory buffer is a technology through which a SSD can "borrow" a small amount of ram from the computer, and work with that amount through pci-e lanes. For example, a typical such memory amount is 64 MB. This is nowhere the full amount that would be needed to keep the whole table of files and where the data of those files is located in memory chips, but segments of that data could be cached in that 64 MB chunk and periodically backed up to flash memory. 

So, you'd get a performance between a drive with dram and a dramless drive. 

 

DRAM helps if you write a lot of small things often and if you use multiple applications that each write to the SSD small amounts of data. 

It doesn't help you boot Windows faster, it doesn't boot applications faster (well, not in any significant way), you have a small benefit when writing lots of data.

 

So I basically say don't worry about it. 

 

I personally went for a Samsung 980 and use it as a boot drive, works perfectly fine. SN750 is a good choice as well  (though keep in mind SN750 SE is dramless, SN 750 has dram). Don't know about teamgroup drive's specs so can't say anything about it.

 

 

[Chris Pratt]

DRAM serves two purposes for an SSD: storing the drive table map and acting as a level one cache.

 

SSDs degrade with writes, so they employ a concept of write leveling to ensure even wear across the drive. However, because of this, data is not always contiguous and the drive needs a map to know where to fetch all the bits for your file(s). DRAM ensures that this table can be quickly accessed. HMB is a feature of NVMe that allows the drive to access a small portion of system RAM for this purpose instead. Using system RAM is nearly as fast, but is more limited, such that only about 50-100GB of the drive can be referenced at once. If you're working with smaller files or not doing a lot of reads, you'll probably never notice the difference, but otherwise, speeds will fall through the floor.

 

SSDs typically use TLC or triple layer cell now, as a trade off between capacity and speed. This means each cell can have three bits written to it, but each successive bit is harder to write than the one before (slower). Particularly as you fill the drive, speeds begin to fall off, so some form of cache is necessary to compensate. DRAM is very fast but limited. SLC cache can be used as well (often in addition to DRAM). That's basically just a reserved portion of the drive that only uses 1 bit per cell, so it doesn't suffer from the slowdown of higher density cells like TLC. It's much slower than DRAM, but still faster than writing to the drive itself. Either DRAM and/or SLC cache can be exhausted and once that happens, speeds will fall off.

 

What it mostly boils down to is how heavily you're using the drive. Most of these things only start to matter when you're doing a heavy amount of reads/writes or doing so over an extended period of time. For small, bursty workloads, it won't matter really if you have DRAM or not.

[mariushm]

5 minutes ago, LAwLz said:

I don't know about the Teamgroup MP33, but the WD SN570 and Samsung 980 are very similar performance wise, with the WD Blue probably being slightly better. I don't think we know for sure since I can't find good reviews for the SN570, but the SN550 (before it was downgraded) was slightly better than the Samsung 980, so the 570 with its upgraded flash should be even better.

 

If all of them cost the same, then I'd go for the SN570 out of those three. The problem DRAMless drives have had historically is that they weren't that much cheaper than the better drives. For example the Samsung 980 wasn't that much cheaper than the 970 EVO, and yet the EVO performed quite a bit better.

 

Samsung 980 has bigger SLC cache, compared to SN750 and SN550  ... WD drives use up to 12 GB of SLC cache, while Samsung 980 uses 45 / 122 / 160 GB (for 250GB/500GB/1TB models).  It's UP TO because as you fill the drive with data, this SLC maximum size will be shrinked. 

Samsung 980 defaults to 64 MB host memory buffer (minimum 16 MB) , while SN550 defaults to 32 MB (minimum 3 MB) and I don't think SN750 has a controller that's capable of host memory buffer feature. 

 

WD drives will fill the 12 GB SLC cache fast, and then speeds will slow down to around 500 MB/s 

Samsung drives will take longer to fill the cache but then speeds will slow down more, to around 350 MB/s 

 

So overall Samsung's 980 behavior would be better for home users as home users will rarely write let's say more than 50 GB in one shot, so the SLC caches will be unlikely to fill to the point where the speeds would drop to the 300-400 MB/s range, but the probability you'd write 10-12 GB is higher, so you'd notice more often speeds dropping to the 500 MB/s range on a WD drive. 

 

From Tom's hardware review of the 500 GB Samsung 980 - write speed over time : 

 

 

Sequential read speeds are also better on Samsung 980  pretty much anytime except when an application reads 128 KB chunks (WD SN550 seems more optimized for that amount) : 

 

[Poraf]

Thanks for all these insights, I think I now have a basic grasp on how dram/dramless works and what I should look for.

[Poraf]

2 hours ago, LAwLz said:

It entirely depend on your use case.

The difference between an SSD with and without DRAM will be that the drive with DRAM will do burst writes much faster than the DRAMless. But since most people don't need extremely fast burst writes on their drives, I'd say that it doesn't matter for most people. And as you mentioned, DRAMless drives can use SLC caches and HMB to help with these bursts.

 

If you want a comprehensive comparison between the drives, you need to look at more than just "does it have DRAM or not". There are way more things that goes into an SSD than just DRAM, and all of them matters for performance.

 

I don't know about the Teamgroup MP33, but the WD SN570 and Samsung 980 are very similar performance wise, with the WD Blue probably being slightly better. I don't think we know for sure since I can't find good reviews for the SN570, but the SN550 (before it was downgraded) was slightly better than the Samsung 980, so the 570 with its upgraded flash should be even better.

 

If all of them cost the same, then I'd go for the SN570 out of those three. The problem DRAMless drives have had historically is that they weren't that much cheaper than the better drives. For example the Samsung 980 wasn't that much cheaper than the 970 EVO, and yet the EVO performed quite a bit better.

 

I recommend you check out some reviews where they compare the drives you are interested in vs some other drives around the same price point, for example the Samsung 970 EVO (plus).

 

I don't know what prices are like where you live, but here in Sweden the Samsung 970 EVO Plus 1TB costs the same as the Samsung 980 1TB, and the EVO performs way better in the tests that matters.

Thanks for this as well. Where I live the Samsung 980 at full price costs about the same as the cheapest dram SSD (that I could find at least) which is the Teamgroup MP34 and Crucial P5, but for some reason dramless SSDs are on sale more often here. Though the SN 570 is just about $5 cheaper than the Samsung 980.