SSD with and without DRAM difference? (and one other question)

[podkall]

What difference does DRAM bring to the SSD?

How much of a hindrance is it if they don't have DRAM?

 

 

Also, is Samsung 970 EVO Plus, DRAM version of 980?

 

or is 970 EVO Plus just faster than 980 and they both are DRAM-less?

[RONOTHAN##]

1 minute ago, podkall said:

What difference does DRAM bring to the SSD?

 

It drastically improves random performance. It's what matters in order to make a drive feel snappy. 

 

2 minutes ago, podkall said:

How much of a hindrance is it if they don't have DRAM?

 

Depends what you're doing. If you're just gonna be doing large sequential file copies or using it as a game drive, it doesn't really matter. If you're going to be using it as an OS drive, it can feel noticeably worse. Get one with DRAM, they're not much more expensive.

 

4 minutes ago, podkall said:

Also, is Samsung 970 EVO Plus, DRAM version of 980?

 

Yes and no. Yes the 970 Evo Plus has DRAM, but the IIRC controller is different than the 980, so it's really a different drive all together. There are 3 main components of a drive: controller, NAND, and cache. If you change one of them, you change the performance characteristics of the drive, and thus its a completely different drive. If your only options are the 970 EVO Plus or 980, get the 970, but there are a number of other similarly performing drives for less money.

[LienusLateTips]

DRAM makes a big difference if you're moving a lot of small files around/using those files. If it's a largely storage drive... you'll be fine without DRAM. Otherwise, I'd get a DRAM drive.

 

The 970 EVO Plus is the second highest tier model in the 970 series, released 2019-2020, with DRAM. The 980 is the lowest end model of their 2021 980 series.

 

The closest thing you have to a DRAM 980 is the 980 Pro. There are other brands making SSDs just as fast/good with PCIe 4.0, I'd check those out too. Examples on the low end being Sabrent Rocket Q4, Adata Gammix S50 Lite. Higher end including Sabrent Rocket 4/4+, Crucial P5 Plus

[podkall]

1 minute ago, LienusLateTips said:

DRAM makes a big difference if you're moving a lot of small files around/using those files. If it's a largely storage drive... you'll be fine without DRAM. Otherwise, I'd get a DRAM drive.

 

The 970 EVO Plus is the second highest tier model in the 970 series, released 2019-2020, with DRAM. The 980 is the lowest end model of their 2021 980 series.

 

The closest thing you have to a DRAM 980 is the 980 Pro. There are other brands making SSDs just as fast/good with PCIe 4.0, I'd check those out too. Examples on the low end being Sabrent Rocket Q4, Adata Gammix S50 Lite. Higher end including Sabrent Rocket 4/4+, Crucial P5 Plus

970 EVO Plus is the "cheapest-more expensive" SSD than 980 from samsung in the e-shop I'm buying from

[LienusLateTips]

Just now, podkall said:

970 EVO Plus is the "cheapest-more expensive" SSD than 980 from samsung in the e-shop I'm buying from

Probably because it's a little bit out of date, but still very fast, one of the fastest PCIe 3 SSDs. 

 

I'd go with the 970 EVO Plus over the 980 any day if it wasn't too much more. Again you shouldn't restrict yourself to Samsung SSDs.

[podkall]

Just now, LienusLateTips said:

Probably because it's a little bit out of date, but still very fast, one of the fastest PCIe 3 SSDs. 

 

I'd go with the 970 EVO Plus over the 980 any day if it wasn't too much more. Again you shouldn't restrict yourself to Samsung SSDs.

it's 24$ more, and I'm not but I figured the next Samsung SSD could have a DRAM cache and I was correct.

 

Would you help me with the SSD if I gave you a list of the ones inbetween 980 and 970 EVO P when it comes to price? (tere's like 16 of them though)

[LienusLateTips]

Just now, podkall said:

it's 24$ more, and I'm not but I figured the next Samsung SSD could have a DRAM cache and I was correct.

 

Would you help me with the SSD if I gave you a list of the ones inbetween 980 and 970 EVO P when it comes to price? (tere's like 16 of them though)

Sure, just send an image or text over in the thread. I'm sure other people would too

[podkall]

8 minutes ago, LienusLateTips said:

Sure, just send an image or text over in the thread. I'm sure other people would too

I'mma write a list here and under it i'll screenshot how they look like if you know some of them.

(cost increasing order)

 

ADATA XPG GAMMIX S11 Pro

ADATA XPG SPECTRIX S20G

GIGABYTE M30

ADATA XPG SX8200 PRO

GOODRAM IRDM Gen.3

Crucial P5

Corsair Force MP510

Team T-FORCE Candera Zero Z340

Patriot Viper VPN110

WD Black SN750

ADATA XPG SPERCRIX S40G RGB

GIGABYTE AORUS Gen4

Intel SSD 670p (same price as 970 EVO)

 

 

 

I see intel is QLC so maybe not that.

 

Edited January 15, 2022 by podkall
edit

[LienusLateTips]

1 minute ago, podkall said:

-snip-

 

Out of these all, probably the Crucial P5. It's a DRAM-equipped PCIe Gen 4 SSD. It's a bit slower than your 980-Pros of the world but it's a good choice.

[podkall]

2 minutes ago, LienusLateTips said:

Out of these all, probably the Crucial P5. It's a DRAM-equipped PCIe Gen 4 SSD. It's a bit slower than your 980-Pros of the world but it's a good choice.

The question is, would it be noticable difference, when it comes to gaming, cause all I will have is stored games there,

 

also if ASUS PRIME B450M-K supports Gen 4 SSDs,

 

if my games are loading portion of game from drive because my GPU is only 2GB would it make a difference?

[LienusLateTips]

2 minutes ago, podkall said:

The question is, would it be noticable difference, when it comes to gaming, cause all I will have is stored games there,

 

also if ASUS PRIME B450M-K supports Gen 4 SSDs

It doesn't support Gen4 SSD, so you'll be limited to ~3200MB/s on PCIe Gen 3.

 

No difference compared to any nicer SSD here. You're limited by the board.

 

Honestly, if you're not utlising the Gen4 support, I'd get something cheaper if it's available. If the price difference is big between the ADATA S11 Pro and the P5, just go for the former.

[podkall]

1 minute ago, LienusLateTips said:

It doesn't support Gen4 SSD, so you'll be limited to ~3200MB/s on PCIe Gen 3.

 

No difference compared to any nicer SSD here. You're limited by the board.

 

Honestly, if you're not utlising the Gen4 support, I'd get something cheaper if it's available. If the price difference is big between the ADATA S11 Pro and the P5, just go for the former.

Which one the S11 or the 980?

Isn't 980 faster than S11 or is S11 better because of the DRAM and 3D NAND?

[podkall]

15 minutes ago, LienusLateTips said:

It doesn't support Gen4 SSD, so you'll be limited to ~3200MB/s on PCIe Gen 3.

 

No difference compared to any nicer SSD here. You're limited by the board.

 

Honestly, if you're not utlising the Gen4 support, I'd get something cheaper if it's available. If the price difference is big between the ADATA S11 Pro and the P5, just go for the former.

Wait, the S11 Pro is 3D and SLC?

That's a huge diff right?

Is S11 worth the 5$ over samsung?

[mariushm]

6 minutes ago, podkall said:

Wait, the S11 Pro is 3D and SLC?

That's a huge diff right?

No, it's 3D TLC memory, Micron 64 layers.  You get higher speeds because 64 layer memory chips are faster than the latest 96/112/128 layer chips  (which are now made because they're more profitable, get more capacity in a chip, but because more layers, you get less overall speed per layer)

 

WD SN750 has dram and also uses the older 64 layer Sandisk / Toshiba 3D TLC and you get decent speeds (3.5 GB/s reads, 2.6 GB/s writes) ...

 

WN SN750SE is dramless and uses other memory chips.

 

A lot of SSDs use some portion of the memory chips in pseudo-SLC mode as a write cache, to improve write speeds.  For example, they take 30 GB of TLC where each TLC cell holds 3 bits, and they switch it to SLC mode where each cell only holds 1 bit ... so you get around 10 GB of SLC memory which is faster and has higher endurance (instead of 2000-4000 erase cycles, you get 8-10k+ erase cycles on this pseudo-slc memory area)

 

On a 500-512 GB SSD, typically a SSD controller will usually have between 12 and 80 GB of pseudo-SLC memory, but of course the amount will decrease as you fill up the drive with data.

But the point is you'll get very fast writes for as long as you fill this pseudo-slc amount and then write speeds will decrease a bit. So for example, you could transfer a 20 GB video to the SSD and you wouldn't notice a performance drop, but do the same with a a 100 GB archive and you may notice speed drop a bit once you go above 50 GB or so... it depends on the SSD.

 

In the case of WD SN750, the cache is set to 12 GB, and once it fills the write speeds drop to around 1.5 GB/s

On a 970 Evo 1 TB, you get around 30-50 GB and then the write speed drops from 2.5 GB/s to around 1.2 GB/s :

 

[podkall]

9 minutes ago, mariushm said:

No, it's 3D TLC memory, Micron 64 layers.  You get higher speeds because 64 layer memory chips are faster than the latest 96/112/128 layer chips  (which are now made because they're more profitable, get more capacity in a chip, but because more layers, you get less overall speed per layer)

 

WD SN750 has dram and also uses the older 64 layer Sandisk / Toshiba 3D TLC and you get decent speeds (3.5 GB/s reads, 2.6 GB/s writes) ...

 

WN SN750SE is dramless and uses other memory chips.

 

A lot of SSDs use some portion of the memory chips in pseudo-SLC mode as a write cache, to improve write speeds.  For example, they take 30 GB of TLC where each TLC cell holds 3 bits, and they switch it to SLC mode where each cell only holds 1 bit ... so you get around 10 GB of SLC memory which is faster and has higher endurance (instead of 2000-4000 erase cycles, you get 8-10k+ erase cycles on this pseudo-slc memory area)

 

On a 500-512 GB SSD, typically a SSD controller will usually have between 12 and 80 GB of pseudo-SLC memory, but of course the amount will decrease as you fill up the drive with data.

But the point is you'll get very fast writes for as long as you fill this pseudo-slc amount and then write speeds will decrease a bit. So for example, you could transfer a 20 GB video to the SSD and you wouldn't notice a performance drop, but do the same with a a 100 GB archive and you may notice speed drop a bit once you go above 50 GB or so... it depends on the SSD.

 

In the case of WD SN750, the cache is set to 12 GB, and once it fills the write speeds drop to around 1.5 GB/s

On a 970 Evo 1 TB, you get around 30-50 GB and then the write speed drops from 2.5 GB/s to around 1.2 GB/s :

 

So should I get the ADATA GAMMIX XPG S11 Pro instead of 980 Samsung?

[mariushm]

You should get whatever is good and cheap and within your budget... within some reasonable limits (for example mines are No QLC drives, just too low endurance and write speeds once the cache is full)

 

If it's for storing movies and games, I'd say just get the 980 or SN550.

 

I'd rather add more money and go for 1 TB SSD, instead of paying 24$ (or whatever in your local currency) more and still get 500-512 GB. A regular person playing games and normal applications won't really "feel" that extra performance, it's a waste of money.

 

edit: I'd have no problems ordering a QLC SSD for an office pc, for example at work the PC is 90% of the time doing Excel spreadsheets and a proprietary application that works with a database on another server.  The performance of the SSD on the local machine doesn't matter so I wouldn't care if it's QLC or not. But for home, it would bother me.

[podkall]

8 minutes ago, mariushm said:

You should get whatever is good and cheap and within your budget... within some reasonable limits (for example mines are No QLC drives, just too low endurance and write speeds once the cache is full)

 

If it's for storing movies and games, I'd say just get the 980 or SN550.

 

I'd rather add more money and go for 1 TB SSD, instead of paying 24$ (or whatever in your local currency) more and still get 500-512 GB. A regular person playing games and normal applications won't really "feel" that extra performance, it's a waste of money.

 

edit: I'd have no problems ordering a QLC SSD for an office pc, for example at work the PC is 90% of the time doing Excel spreadsheets and a proprietary application that works with a database on another server.  The performance of the SSD on the local machine doesn't matter so I wouldn't care if it's QLC or not. But for home, it would bother me.

Well I either get the 980 Samsung or S11 Pro ADATA which is only 5$ more expensive,

S11 apperently has slightly slower write but faster read, has a cooler,

980 is TLC S11 is 3D TLC,

S11 has SLC cache, 980 has no cache?

 

So by definition is S11 better?

 

(also for WD it's not SN550 it's SN750)

 

edit: What makes WD better if you were looking at the right model?

Edited January 15, 2022 by podkall
edit

[Chris Pratt]

Part of the confusion is that DRAM is dual purpose on a SSD. It is used both to store a map of the contents of the drive and to cache writes.

 

For the first part, SSDs work a lot differently than more traditional storage like HDDs. On an HDD for example, when data needs to be written, it just advances to a free sector and writes the data. As long as you don't delete anything, the data remains mostly contiguous, but since that's not really a real world scenario, the data often gets fragmented over time, and that's why you would do the whole periodic defragmentation routine, so that the data would be more sequential on the drive, and thus a bit speedier for access.

 

SSDs differ in that they are generally MLC, or multiple layer cell, with TLC (triple layer cell) and QLC (quad layer cell) being the most common variations. SSDs also degrade the more writes that are done, particularly so with deletions. In order to both ensure speedy access and longevity, data is intentionally written out of order for wear leveling across the drive and to fill each cell layer sequentially, since it's much harder and thus slower to write each successive bit to a cell. Since the data is all over the place, the drive needs a lookup table to know where to get all the pieces necessary for a particular file or whatever.

 

DRAM is usually large enough to store the map for the entire drive and is extremely fast for doing lookups, both of which aid the speed of accessing all your drive's data as efficiently as possible.

 

A lot of DRAMless drives like the 980 rely instead on HMB (host memory buffer) to store the map. This allows the drive through NVMe to access a small portion of system RAM. Using system RAM is not as fast as dedicated drive DRAM, but it's still speedy. Where it really falls down is in capacity. At the upward limit the drive can access 64MB of RAM which normally gives it enough to map about 50-100GB of a drive at once. The drive will swap in and out the map for the portion of the drive that's being actively used, so it works a little like caching. When you have a cache hit (what you need to access is in the map that's loaded into system RAM), performance is about as good as DRAM would be. However, when you have a cache miss, performance drops through the floor. This makes DRAMless drives with HMB just fine for things like gaming or just general work, since you'll usually always be within that mapped area of the drive. Even with games that's are 150GB+, which obviously exceeds the addressable limit, you're generally only actually working with 50GB or less at a time for the particular map or area your in, so it works out. They are awful for any sort of extremely large files or workloads where there's a ton of data access, though.

 

Now, for DRAM as write cache. As mentioned, SSDs typically store multiple bits per cell and each successive bit is harder to write than the last. That means that as the drive begins to fill, speeds can drop off significantly. As such, a cache is usually employed to buffer the writes at a high speed, so they can then be spooled to the actual drive storage in the background. SLC (single layer cell) cache is most common, which is as fast as NAND storage can be, but still much slower than something like DRAM. However, SLC cache is usually much larger than DRAM cache, though still limited. As such DRAM works great for short, bursty workloads, but falls down with extended or large writes. It's not necessarily an either or thing. Usually DRAM will simply be used as a first tier cache, alongside SLC cache for larger, heavier writes, so DRAM is beneficial here, but not strictly as necessary as it is for the drive map.

 

The long and short is that if you want fast random access, you need DRAM. If you're using the drive more casually for mostly stable storage and only using 50-100GBs of data at once, you can get by without DRAM and be just fine. None of these solutions are perfect, though, so you will sometimes get drive slowdowns, particularly as the drive fills and more layers have to be written to the cells. QLC, in particular, is a worst case scenario for this as they fourth bit is exponentially harder to write to. The only real benefit to a QLC drive is that you can get higher capacity SSDs than you otherwise would be able to. However, there's many manufacturers that use QLC for small budget drives, and those should be avoided.

 

[podkall]

8 minutes ago, Chris Pratt said:

 

So which one would you choose or recommend me?

I wrote some info right above your comment between 980 and S11

[Chris Pratt]

6 minutes ago, podkall said:

So which one would you choose or recommend me?

I wrote some info right above your comment between 980 and S11

Neither are the best choice, but the S11 would be better for random access and larger sustained writes, while the 980 would be better in most other casual usage scenarios. The 970 Evo Plus would be far better than both, and is virtually the best Gen3 drive on the market. The WD SN750 is a close second.

[mariushm]

Is it that hard to find some reviews and look through them?

Samsung 980 has SLC caching, it just doesn't advertise it because pretty much everyone does it, so it's nothing special

Heres a review for the gammix s11 pro  (it's for the 1 TB model, but you can sort of extrapolate for the 512 GB model) :  https://www.tomshardware.com/reviews/adata-xpg-gammix-s11-pro-m2-nvme-ssd/2

Scroll down and you see there the 1 TB model can sustain up to around 160 GB of writes until the slc cache fills, then speed drops to less than 1 GB/s ... if you keep writing at around 670 GB mark, speed drops to 540 MB/s

BUT you wouldn't care about this ... unless you constantly have to write very big files on the SSD.

Let's say you download or install a 50 GB game ... you would never notice any speed drop because the 160 GB threshold is not reached. Note that it's only valid for the 1 TB model - the 512 GB model will probably have 60-80 GB of SLC memory. 

IN comparison, the WD SN750's write speeds would drop to 1.5 GB/s after the first 12 GB/s but after that it will keep at 1.5 GB/s and won't degrade further (as opposed to this drive that drops to 0.9 GB/s and then to 0.5 GB/s)

 

 

 

Here's the Samsung 980  review : https://www.tomshardware.com/reviews/samsung-980-m2-nvme-ssd-review/2

 

And luckily it's compared to WD SN550 as well :

The review points out that it can do up to 100 GB of SLC cache, and you get 2.5 GB/s but once the cache is filled, speed drops to around 350 MB/s ... which is worse than SN550 which has much lower cache, but will sustain around 500 MB/s

Either way, it doesn't matter, as you're unlikely to write tens of GB often.

Within seconds or minutes of you being done writing, the SSD starts emptying the write cache and moving data to permanent locations in TLC memory. The review says after a minute, 30 GB of SLC cache was available again.

 

 

 

 

So the moral of the story ... strictly looking at the pretty graphs, Gammix S11 Pro is a bit better than 980  but in real world usage, you wouldn't notice that performance drop, as you'll RARELY write 50 GB+ of data in one shot.... and the one time where you would have to write 100 GB or more in one shot, it wouldn't be that time critical that you'd mind that it takes 10-30s more to complete copying 200 GB.  And read speeds are not affected.

 

 

 

[podkall]

7 minutes ago, mariushm said:

 

SSD that can write in 3GB/s suddenly droping a whole gig of speed sounds scary tbh

 

but I guess it's not applicable to gaming,

 

here's a question, you say the cache changes based on the drive's used capacity,

 

what if the SSD was filled to like 480GB  out of 500

 

is that noticable in games or not at all?

[mariushm]

6 minutes ago, podkall said:

here's a question, you say the cache changes based on the drive's used capacity,

 

what if the SSD was filled to like 480GB  out of 500

 

is that noticable in games or not at all?

Write speeds would be affected, not read speeds. But writing big files, not basic stuff like saving a game.

Read speeds would be unaffected, so loading games, stuff like that, won't notice any change.

 

And you'd wear out the SSD a bit faster if you constantly write stuff in that remaining 20 GB, delete, write something new, delete and so on ... 

 

It's always a good idea, to leave at least 5% of the drive empty, preferably 10%.

 

PS.  The SLC cache size would also decrease as you fill the drive with stuff

For example, say the Samsung 980 has 100 GB of SLC cache .. that is spread across the memory chips. So as you fill the drive, portions of those memory chips can no longer be used for SLC cache .. so let's say if you fill 100 GB of the drive, you'll only have a maximum of 80 GB of SLC cache, and so on .. at 400 GB of capacity used, you'd probably have only 10-20 GB of SLC cache.

[podkall]

2 minutes ago, mariushm said:

Write speeds would be affected, not read speeds. But writing big files, not basic stuff like saving a game.

Read speeds would be unaffected, so loading games, stuff like that, won't notice any change.

 

And you'd wear out the SSD a bit faster if you constantly write stuff in that remaining 20 GB, delete, write something new, delete and so on ... 

 

It's always a good idea, to leave at least 5% of the drive empty, preferably 10%.

Which is why comes a question if S11 would be better "somehow" since S11 has a 3D NAND,

 

if the 3D nand even makes a difference.

 

So if I get 480GB used but won't install any more games, only their updates,

 

just looking a the worst case scenario point of view.

[Chris Pratt]

40 minutes ago, podkall said:

SSD that can write in 3GB/s suddenly droping a whole gig of speed sounds scary tbh

 

but I guess it's not applicable to gaming,

 

here's a question, you say the cache changes based on the drive's used capacity,

 

what if the SSD was filled to like 480GB  out of 500

 

is that noticable in games or not at all?

The chart was specifically for sustained writes. All the drives fall off, because this is basically a worst case torture test for any SSD. The point is the exhaust all forms of cache, so you hit the raw bare metal speed of the drive, and that's it. If anything, this shows why cache is so important for SSDs. In practical use, you'd likely never see anything this dramatic.