840 evo write speed starts fast then slows down (how can i fix?)

[Valkyrie743]

Hey all. so i picked up a used 840 evo and noticed that its write speeds are not what i thought they would be. i already know about the 840 evo read issues. i have already updated the firmware and also run advanced optimization. 

when i copy files from my other ssd (512gb crucial mx100 ssd) speeds start out fast around 480-495 mbps then it almost halved to 279mbps and stays there. if i copy the same files from my 960 evo 240gb nvme drive to the MX100 its locked rock solid at 485mbps writing. 

I understand these are different drives but still, why is my 840 evo dropping write speeds while my mx100 is not? is it a drive issue or could it be the ssd controller is getting to hot some hot and its throttling speeds? i noticed that when copying a large file my mx100 to my nvme 960 evo that it did the same thing as the 840 but much worse. it speeds were at 510mbps then dropped to 120mbps  crystal disk info was showing the drive temp hitting 44C for the 960 evo nvme. don't think that's very hot for a drive?. 

here is a picture of the copy from the mx100 to the 840 evo.  

[dfsdfgfkjsefoiqzemnd]

Just copied a 19GB file from my 960 PRO (512GB) to my 840 EVO (1TB) as a test.

 

My graph isn't as fancy due to using Win7, but in the screenshot I'm at the end of my copy and still showing 500+.  It dipped to 499MB/s in the very last second, so nowhere near the <300 you are getting.

 

 

Crystal Disk Info is showing 26.5K power-on hours for mine, with 46TB written.

 

How full is your 840?  If it's close to full, that may slow it down a lot. 

Also it may slow down when it's copying a lot of smaller files versus a single large one.  so use the exact same file(s) to compare speeds. 

 

Oh, as for the temps of your 960 EVO, those are absolutely fine.  Samsung recommends keeping it between 0°C and 70°C.  

[Valkyrie743]

I just tried with a 1080P MKV that was 26gb.  from my 960 to the 840 evo and same speeds  

do you have that samsung turbo cache feature enabled?

 

 

2 hours ago, Captain Chaos said:

Just copied a 19GB file from my 960 PRO (512GB) to my 840 EVO (1TB) as a test.

 

My graph isn't as fancy due to using Win7, but in the screenshot I'm at the end of my copy and still showing 500+.  It dipped to 499MB/s in the very last second, so nowhere near the <300 you are getting.

  Reveal hidden contents

 

Crystal Disk Info is showing 26.5K power-on hours for mine, with 46TB written.

 

How full is your 840?  If it's close to full, that may slow it down a lot. 

Also it may slow down when it's copying a lot of smaller files versus a single large one.  so use the exact same file(s) to compare speeds. 

 

Oh, as for the temps of your 960 EVO, those are absolutely fine.  Samsung recommends keeping it between 0°C and 70°C.  

[dfsdfgfkjsefoiqzemnd]

6 hours ago, Valkyrie743 said:

do you have that samsung turbo cache feature enabled?

I don't.  If I were to enable that option the numbers would be a lot higher.  I have enough RAM to handle the whole movie file, so I'd basically get the full 3500MB/s of my NVMe drive throughout the transfer. 

 

I would suggest attaching the drive to another SATA port and cable, to see if that helps.  Beyond that I'm out of ideas. 

If it were the slowdown issue that the 840 EVO is known for, you'd be having slow read speeds but the write would be unaffected.  That is clearly not the case here.

[Spotty]

I tried with my Samsung 840 evo, transferring 5GB, 10GB, and 20GB files from a 970 evo. The transfer would start out at around 490MB/s and then for the larger files eventually it would jump down to around 420MB/s before finishing. It was a pretty sharp drop off, going from 490MB/s to 420MB/s pretty much instantly once it reached a certain point in the transfer.


 

Spoiler

idk what's going on with the huge spike at the start, transfer initially starts out showing 1500MB/s for about a second or two then goes down to ~490MB/s, stays there for a while, then drops down to 420MB/s about half way through the transfer.
Cache? SLC write buffer? Windows not knowing how to calculate things? ¯\_(ツ)_/¯

 

When I go the other way, Samsung 840 Evo to Samsung 970 Evo, it's a consistent straight line staying between 488-492MB/s (read speeds from 840 evo). So probably not a windows issue then, maybe caching/SLC write buffer.

I transferred the 20GB file back to back a few times, to try and get the temps up a bit, saw temperatures rise from 41C to 51C, and eventually the write performance on the 840 evo started dropping down to around 380MB/s. So it's possible there was a little bit of performance loss due to thermals (throttling), but not as much as severely as what you're seeing.

[dfsdfgfkjsefoiqzemnd]

23 minutes ago, Spotty said:

idk what's going on with the huge spike at the start, transfer initially starts out showing 1500MB/s for about a second or two then goes down to ~490MB/s, stays there for a while, then drops down to 420MB/s about half way through the transfer.
Cache? SLC write buffer? Windows not knowing how to calculate things? ¯\_(ツ)_/¯

That's probably the 840's "TurboWrite Cache" (as Samsung calls it) filling up indeed.  Once the drive's cache is full, you'll suddenly see the speed drop off to the drive's actual write speed.  I'm also seeing much higher write speed numbers early on in the transfer. 

 

NOTE : TurboWrite is not the same as the "Rapid Mode" that the Samsung Magician software gives you. 

TurboWrite uses NAND from the SSD itself, Rapid Mode uses your PC's RAM as an even faster buffer.

[Valkyrie743]

Spoiler

 

11 hours ago, Spotty said:

I tried with my Samsung 840 evo, transferring 5GB, 10GB, and 20GB files from a 970 evo. The transfer would start out at around 490MB/s and then for the larger files eventually it would jump down to around 420MB/s before finishing. It was a pretty sharp drop off, going from 490MB/s to 420MB/s pretty much instantly once it reached a certain point in the transfer.


 

  Reveal hidden contents

idk what's going on with the huge spike at the start, transfer initially starts out showing 1500MB/s for about a second or two then goes down to ~490MB/s, stays there for a while, then drops down to 420MB/s about half way through the transfer.
Cache? SLC write buffer? Windows not knowing how to calculate things? ¯\_(ツ)_/¯

 

When I go the other way, Samsung 840 Evo to Samsung 970 Evo, it's a consistent straight line staying between 488-492MB/s (read speeds from 840 evo). So probably not a windows issue then, maybe caching/SLC write buffer.

I transferred the 20GB file back to back a few times, to try and get the temps up a bit, saw temperatures rise from 41C to 51C, and eventually the write performance on the 840 evo started dropping down to around 380MB/s. So it's possible there was a little bit of performance loss due to thermals (throttling), but not as much as severely as what you're seeing.

 

 

so you get the same thing but no where as near as mine. guess my drive has more ware to the nand flash maybe causing slow writes.  i tried different sata ports with no help. i think its just the drive. i noticed that if i open crystal disk mark i  get no errors but if i open hd tune pro i get these errors. would this be why my write speeds are lower?

[dfsdfgfkjsefoiqzemnd]

CRC error count is no big issue.  If the previous owner had a bad (or badly seated) SATA cable at some point, that could have caused those errors to happen.  Doesn't mean there's any CRC-related problems now.

 

The "Used Reserved Block Count" is puzzling.  There's no way that your drive's NAND is worn already, so that can't explain the drive running out of reserve blocks.  It may be faulty though.

 

A bit of Googling (actually DuckDuckGo-ing) reveal that this can happen sometimes.  It could be a simple matter of the drive reporting the wrong data or it could be an actual hardware problem. 

This is the first thread I came across that ended up being resolved: https://www.hwinfo.com/forum/Thread-Solved-840-EVO-1TB-warning-failure

The poster from that thread contacted Samsung about this and had they replaced the drive based on that one S.M.A.R.T. value.  However that thread is from 2016, which was most likely within the drive's warranty period.  I wouldn't count on getting the same offer if you contact them now. 

It never hurts to try though, you may get a good deal on a more modern equivalent. 

 

FYI my 840's Used Reserve Block Count is 100 100 10, so that "1" you are getting is definitely not a normal value.