Question SSD Write speed drops to 30MB/s after download

Mariachi

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Apr 8, 2016
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I have 240GB Lexar NQ100 SATA SSD and it has still 130GB free, however write speed dropped down to 30MB/s from original 500MB/s.

Its also partitioned into two 40GB and 183GB partitions.

If i delete about 20 GB of space write speed goes back to normal, what causing this?
 

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mikeymikec

Lifer
May 19, 2011
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Presumably the 'deleting 20 GB of data' bit is regarding the 183GB partition? How full is each partition?

Out of curiosity, why did you benchmark the drive in the first place, were you seeing some kind of performance-related symptom?
 

Mariachi

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Apr 8, 2016
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Need to copy another 20GB on SSD and i wonders should i buy new SATA SSD, because all of them have this issue so i will have to buy 500GB SSD to effectiveley use 250gb?



1649160471001.png



Out of curiosity, why did you benchmark the drive in the first place, were you seeing some kind of performance-related symptom?
Because i see slow write speed in windows when i copy files over to SSD, only 30/MB when normally its 300MB/s or more.

I have same HDD in my older laptop and same problem if around half of HDD is full and i copy files to SSD my whole OS freeze and lagging until copy is finished.

I've been trying to figure out the problem ever since, no one was able to give me answer.
 
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mikeymikec

Lifer
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Does the transfer speed start at ~300MB/sec then drop to 30MB/sec part-way though?

Where is the data being transferred from?
 

Justinus

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Oct 10, 2005
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This sounds like TLC write cache issues. 30MB/s may be the drive's direct to TLC write speed, and it may have firmware bugs with regards to clearing the pSLC cache (or maybe it's an extremely small cache in the first place and your large file copies fill it up quickly).

You could try downloading the Lexar SSD Dash and seeing if there are any firmware updates for the drive.


Need to copy another 20GB on SSD and i wonders should i buy new SATA SSD, because all of them have this issue so i will have to buy 500GB SSD to effectiveley use 250gb?
The reality is the vast majority of SSDs are pSLC cached TLC or QLC and if you want to store 250GB of data and fill up all the space on a 240/250GB SSD there is no spare room for pSLC caching to take place, and it causes write amplification trying to juggle around your writes between the scarce open sectors.

Typically to maintain good performance and minimize write amplification you need to overprovision around 10% of your drive's capacity to ensure there is always sufficient space to use for dynamic pSLC caching, write operations, and garbage collection.
 
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Tech Junky

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Jan 27, 2022
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A couple of things.

Just get a 1TB drive and skip the hassel with performance issues due to space ratios.

Make sure you check the firmware for updates. I had one based on a phison controller that had speed issues until I updated the firmware.
 
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mikeymikec

Lifer
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I haven't been able to find out the information I wanted about the drive you're using but reviews describe it as a very cheap, low-end drive. My guess is that a few factors are coming into play such as minimal SLC caching (possibly due to the lack of available space on the drive, resolved once you clean up some space) and no DRAM cache.

I understand a bit more about the SLC to TLC scenario, not so much about DRAM-less SSDs, just that my experience of the latter is that system responsiveness goes to pot during a large data transfer to such a drive.
 

Tech Junky

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DRAM makes a difference on bursty transfers to the limit of the cache.
Space ratios play into the speed over longer duration transfers.

Once you hit 75-80% of the capacity there's less room to move the bits around and forces the drive / controller to slow the speeds to place bits into specified areas vs bulk moving to the drive and doing housekeeping later.

On the NVME side I've not really seen too many issues with slowdowns over longer moves. There are some benefits with some implementations over others. Controllers / DRAM do make a difference to an extent though. When moving files between my BPX Pro and CS3140 I can see a difference going from 1GB/s to the other direction 1.5GB/s. So, one drive is cable to WR 50% faster than the other. Does it make a difference in real world performance? Not really as the drives are mostly idle due to just how fast they pull and push data. Even loading a game they might hit 5% which is nothing. The impacts come when moving a huge amount of data at a time.

SATA being limited to 600MB/s though levels the playing field as NVME drives range from Gen3 1500MB/s up to Gen4 close to 7500MB/s and there's no real standard being applied to min/max other than limitations based on the controller, dram, ram chips.

Pulling from a legacy HDD @ 98MB/s should be a one time deal unless planned to use it as a backup destination. Newer SATA drives hit 200MB/s+ at this point. On my server setup I can hit 225-250MB/s using 5400's and 7200's can hit even higher but, aren't worth the costs IMO. If speed is the concern then upgrading to SSD performance would be more logical than a 7200 which just increments the speed and produces more heat in the system.
 

mikeymikec

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May 19, 2011
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I've only had the one experience, brand new laptop with a DRAM-less NVMe SSD, and I was in the middle of a ~130GB transfer of mixed file sizes to the drive (from a USB 3.1 mSATA SSD). As expected I experienced the drop in transfer speed after a while, but also I attempted to continue setting up the laptop during the transfer, and the responsiveness was poor enough for me to treat the machine like it was booting from a HDD, give it one job to do at a time and just wait.

The rest of the laptop spec was no slouch either - Ryzen 5 3500U / 8GB RAM. Internal SSD usage was at 100% in Task Manager though, where normally I'd expect a better SSD to be certainly less than 50% usage and system responsiveness to be normal.

The source drive's usage was pretty minimal too. The internal SSD wasn't reporting any issues (e.g. SMART / event log).
 

Mariachi

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Apr 8, 2016
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There's no firmware update available trough SSD Dash.

Typically to maintain good performance and minimize write amplification you need to overprovision around 10% of your drive's capacity to ensure there is always sufficient space to use for dynamic pSLC caching, write operations, and garbage collection.
So far i have almost 50% of space free


DRAM makes a difference on bursty transfers to the limit of the cache.
Space ratios play into the speed over longer duration transfers.
I heard there is software to use RAM for caching for SSD could you recommend a few to try?

Untitled.png
 
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IntelUser2000

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I heard there is software to use RAM for caching for SSD could you recommend a few to try?
DRAM buffers aren't caches for SSDs but map sections of the flash to track addresses for garbage collection. They usually map 1024:1, meaning 1GB of DRAM for 1TB of flash.

That drive doesn't have DRAM. That's the reason it's slow. You'll need to allocate far more space and you'll still have noticeable performance losses.

Don't get a DRAM-less drive next time.
 
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Mariachi

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but DRAM buffer is only good for the size of the dram e.g. DRAM 512MB would not help with file that is bigger 1024MB and i would still experience same slowdown?
 

IntelUser2000

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but DRAM buffer is only good for the size of the dram e.g. DRAM 512MB would not help with file that is bigger 1024MB and i would still experience same slowdown?
You didn't understand me. Read again carefully. DRAM buffers are NOT caches for SSDs. They handle the "garbage collection" which allows it to keep performance. It keeps data for tracking such things. That's why you only need 1GB. They do not keep program data.

What YOU refer to is called a cache. DRAM buffers are NOT caches in a typical sense.

This is why all the high end/high performance SSDs have it. DRAM-less SSDs handle the duty in NAND, which is 1,000-10,000x slower in latency.

I would say arguably DRAM-less are worse than decent HDDs, as our senses are relative and while HDDs consistently slow, DRAM-less ones will feel fast but screech to a halt.

It's like a race car going through city traffic and traffic lights. It's super fast for a brief moment, but it stops. A normal car will feel much smoother.
 

igor_kavinski

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It feels like typical price cutting tactics from the USB flash drive world being introduced to the world of internal SSDs. Because it's so easy to sell crap to unwitting consumers.
 
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igor_kavinski

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Yeah. Intel so failed in trying to cut costs that way that they sold their NAND business to SK Hynix.

Intel maps out Optane’s future and says Penta Level Cell NAND is in the works (pcworld.com)

Intel says floating-gate cells will also aid its PLC designs. It’s hard to confirm that, but reports have suggested that Micron split from Intel because Micron wanting to dump floating gate for charge trap. While most companies use charge trap designs today, Toshiba is apparently looking at floating gate for its PLC designs. We won’t have any hard answers for a year or two.
Micron was probably right but Intel's engineers are so sure of themselves and their projections. In the end, they likely figured, let's try to fix one failure at a time (CPUs) and unloaded the NAND business.
 

IntelUser2000

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@igor_kavinski Intel might be right about Floating Gate vs Charge Trap decisions, but the whole company doesn't like the memory business. Their main business was the memory business until Andy Grove steered them away and into the CPU business as their main bread and butter. They became so successful after that it almost became an icon of why Grove was such a great CEO.

The mentality continues with Pat as he recently stated his dislike about the memory business. This tells why they have become quiet about Optane and went away from eDRAM. Although for now they'll keep Optane going.

DRAM is an area where not only it's cutthroat but without having majority share like Samsung does your margins will be really low. NAND probably reached that point some time ago. Since they practically started the SSD era with X25-M in 2009 and is a necessary driver for computers, in the end they are winners either way.

It feels like typical price cutting tactics from the USB flash drive world being introduced to the world of internal SSDs. Because it's so easy to sell crap to unwitting consumers.
This is why I think it's very good to compare things in a normalized fashion. Things like "solid state is more reliable and faster" "mechanical is unreliable" is only true when the former is more pricier than the latter.

If/when some SSDs can reach price point of future HDDs, I pretty much guarantee you it'll be a toss up between HDDs and SSDs in terms of reliability and performance. Actually the way some SSDs are, some are less reliable than HDDs are. Their often abrupt nature of failing is worse than the way lots of HDDs fail which are far more graceful and allow you to recover data much easier.

You look at laptop repair videos and ton of them talk about data recovery and SSD failures. TBW is one metric, but you still have moisture/dust induced damage, component failures, PCB damage.

As an engineer you always get to choose your focus. If you want the lowest cost with in paper the most reliable technology, you won't get that.
 
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Mariachi

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Apr 8, 2016
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Bought Crucial MX500 500GB it had 500MB DRAM so far works full speed, however with the LEXAR i am still amazed what is going on.

Merged all partitions and made SSD alignment using AOMEI Partition manager then run the test.

CrystalDiskMark_20220408142902.png
 

Mariachi

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Apr 8, 2016
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You didn't understand me. Read again carefully. DRAM buffers are NOT caches for SSDs. They handle the "garbage collection" which allows it to keep performance. It keeps data for tracking such things. That's why you only need 1GB. They do not keep program data.
I am more of a visual learned, could you draw a diagram for me if that's okay?



This is why all the high end/high performance SSDs have it. DRAM-less SSDs handle the duty in NAND, which is 1,000-10,000x slower in latency.
I did not experience any slowdowns until write speed capped at 30MB/s after SSD got close to being 40% full.
 

IntelUser2000

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I am more of a visual learned, could you draw a diagram for me if that's okay?
Caches store program data. Your programs might be gigabytes in size. Of course it doesn't need to store the entire program, but just what is required. For example in games it might store previously rendered frames, which are easily in the MB range.

SSDs do what's called "garbage collection". The NAND chip used in SSDs need to delete data before it can rewrite to it's storage cells. The deletion process is really slow.

Therefore, what garbage collection process does is it tries to spread stored data around to every other cell that hasn't been already used. During times of idle for example, it takes the time to delete the cells it's been used, so your performance won't tank. It doesn't just do it while idle. Some active management exists.

The DRAM buffer only keeps data about location of cells on an SSD and what the state of the cells are whether they are clean or dirty. That's why it only needs 1GB for 1TB SSD. It knows absolutely nothing about the programs, not even their name since it doesn't need to.

In a magnetic hard drive, the physical location of the data in the drive is same as the logical(the way you/program sees it) location. In an SSD, there's no relation between physical location and logical location because of the requirements of garbage collection.
 
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Mariachi

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Thanks for explanation.

I formatted Lexar SDD and still having very slow performance, when i bought it month ago was fast, screenshot in first message.

Perhsaps i need to erase all data on SDD somehow because deleting partition did not do enable garbage collection mechanism? What tool can i use to clean it?
 

mikeymikec

Lifer
May 19, 2011
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Perhsaps i need to erase all data on SDD somehow because deleting partition did not do enable garbage collection mechanism? What tool can i use to clean it?
AFAIK garbage collection is a mechanism controlled entirely by the SSD so there's no checking/triggering that manually per se. However on your Win10 installation you can run the defrag utility which should give you the option to 'optimise' your SSD (ie. run TRIM). It ought to be running automatically though on the default Win10 settings.

Win7 isn't SSD aware so it doesn't have the optimise option.
 
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IntelUser2000

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Yes, as @mikeymikec mentions, TRIM will help with that.

It depends on the algorithm the controller uses and you may be able to trigger it manually but that's a shot in the dark even if it was possible.

TRIM is the way to go since you have an SSD. Depending on the SSD, even something as often as weekly schedules will help. I have a cheap Silicon Power SSD that shows noticeable performance degradation in less than a week. DRAM-less of course.

DRAM buffer SSDs slow down too but not as drastic and takes longer to reach that level.
 
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Mariachi

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Apr 8, 2016
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Does Win10 TIMS all data, it took under 10 seconds to run this trim.

Is there third party tool to make thorough TRIM?

1.png
 
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