SSD to NVME transfer speeds

[vooo]

I am struggling to get transfer speeds of over 100mb/s between my SSD and NVME. Today I transfered some files from one drive to the other via unbalance and averaged 87MB/s this seems really low and I feel that I have a setup issue which is causing this but I do not know what. I feel like this should be 5x faster, I have the SSD in a 2 disk array with no parity or cache drives. any advice would be appreciated.

[PeteAsking]

87 MB/s is like 700 megabits per second so maybe start with what the ssd read speed is rated at and tell us (assuming you copied from ssd to nvme). 

[vooo]

SSD read speed is 550MB/s its an evo 860

[testdasi]

On 6/29/2020 at 12:53 AM, vooo said:

I am struggling to get transfer speeds of over 100mb/s between my SSD and NVME. Today I transfered some files from one drive to the other via unbalance and averaged 87MB/s this seems really low and I feel that I have a setup issue which is causing this but I do not know what. I feel like this should be 5x faster, I have the SSD in a 2 disk array with no parity or cache drives. any advice would be appreciated.

Your post lacks details. How do you do the transfer? Over what network? What are the brand model capacity of the disks involved? What sort of files are being transfered? etc.

 

Also your setup of having only 2 SSD in the array with no cache is rather questionable. The NVMe, for instance, is a prime candidate to be in cache.

[Energen]

You are filling up the NVMe's cache which then causes it to slow down because it has to directly write to the drive, rather than the faster cache.

 

I'm not going to get into it again here since this has been a recent topic but you can see some other threads in my activity feed about NVMe speeds. 

 

Seems like NVMe is great, if you don't actually use it for anything... then it's just another slow drive.

[testdasi]

9 hours ago, Energen said:

You are filling up the NVMe's cache which then causes it to slow down because it has to directly write to the drive, rather than the faster cache.

 

I'm not going to get into it again here since this has been a recent topic but you can see some other threads in my activity feed about NVMe speeds. 

 

Seems like NVMe is great, if you don't actually use it for anything... then it's just another slow drive.

Hmmm I regularly get 900+ MB/s throughput with my NVMe and it's an old Intel 750, the first consumer widely available NVMe drive, with 261TB already written, and counting.

 

I think you are making generalised sweeping statement that doesn't quite help the OP specific case. As I said on the previous post, the OP offered scarcely any details which may point to what can be wrong.

[Energen]

4 hours ago, testdasi said:

I think you are making generalised sweeping statement that doesn't quite help the OP specific case. As I said on the previous post, the OP offered scarcely any details which may point to what can be wrong.

You are ignoring all the technical limitations of the hardware.  In both recent threads about speeds you've asked about "how" the files are being moved or are concerned with the type of drive while not taking into consideration how the drives actually operate. 

 

I'm no expert at SSD speeds but when the evidence is plainly spelled out by manufacturers it's hard to expect anything more.

 

Samsung SSD "up to" 520MB/s write speed.. "The sequential write performances are measured with Intelligent TurboWrite technology being activated. The sequential write performances may not be sustained for the portion of data exceeding over Intelligent TurboWrite buffer size."

 

 

That's quite a difference from the advertised speeds.  And if he were writing to the 860, he's got write cache of only 512MB up to 4GB depending on the model, then everything slows down.  Same with whatever NVMe he's using.

 

I agree that the OP should provide more details, but from what I've been seeing while researching this issue I don't think any details about the hardware or how the files are being moved is going to make a difference.  There's a physical limitation to the drive.  And how far should you drill down on the hardware?  What if the SSD and the NVMe are sharing the same PCI-E lane?  How would that affect the speeds?

 

Maybe I'm wrong, and I'm open to being schooled, but there's enough evidence out there that suggests all forms of SSDs/NVMe's aren't as great as you'd expect them to be.

[testdasi]

1 hour ago, Energen said:

I agree that the OP should provide more details, but from what I've been seeing while researching this issue I don't think any details about the hardware or how the files are being moved is going to make a difference.  There's a physical limitation to the drive.  And how far should you drill down on the hardware?  What if the SSD and the NVMe are sharing the same PCI-E lane?  How would that affect the speeds?

 

Maybe I'm wrong, and I'm open to being schooled, but there's enough evidence out there that suggests all forms of SSDs/NVMe's aren't as great as you'd expect them to be.

You quoted information about the 860 QVO, the OP said he has a "EVO 860". Evo is TLC, QVO is QLC. Major difference.

 

From the time that I have started using SSD when TRIM just became a thing (a Kingston 128GB model that was on SATA II), up to when I started using M.2 PCIe SSD when NVMe wasn't even a thing (many don't even know there was a time that M.2 and NVMe are not necessarily the same thing), up to getting the 1st widely available consumer NVMe (Intel 750), up to moving fully towards solid state storage for all my critical data, up to right now when I'm rocking 3x Optane SSDs, I have read up a lot about SSD's and how to maximise their performance.

 

Hence my experience allows me to know or at least make good prediction about the kind of performance to be expected.

With that knowledge, I made the assessment that 87MB/s is unusually slow.

Hence I ask for more details in the hope of finding out where the bottleneck is to help to OP, instead of making a sweeping generalised statement.

 

 

Models matter. Technology matters. What kind of files being transferred matters. Copying using cp vs using mc matters. DD with dsync vs without dsync matters. Heck, even the file system of the SSD matters.

TL;DR: details matter.

Edited July 11, 2020 by testdasi

[Energen]

55 minutes ago, testdasi said:

You quoted information about the 860 QVO, the OP said he has a "EVO 860". Evo is TLC, QVO is QLC. Major difference.

2 hours ago, Energen said:

And if he were writing to the 860, he's got write cache of only 512MB up to 4GB depending on the model.

The graphic was from the QVO, the information was for the EVO, since details matter.  The point was that actual real world speed is different than what is advertised.

 

https://www.samsung.com/semiconductor/minisite/ssd/product/consumer/860evo/

 

CACHE MEMORY

512MB Low Power DDR4 SDRAM
(250GB, 500GB)
1GB Low Power DDR4 SDRAM (1,000GB)
2GB Low Power DDR4 SDRAM (2,000GB)
4GB Low Power DDR4 SDRAM (4,000GB)

 

Perhaps you need a refresher on SSD, here's an article that explains why TLC is slow.  It's 5 years old but still relevant.

https://www.pcworld.com/article/2998497/tlc-nand-ssds-the-crippling-problem-storage-makers-dont-advertise.html

 

Anyways, you've got your opinion, I've got mine. Neither of us will agree on them for sure, and none of it helps the OP. I'm out of this discussion.