Question New M.2 NVMe - very slow writing

GeorgiaOverdrive

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May 30, 2014
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I got a new computer that came with a 2TB M.2 MVMe, and it has good benchmarks with Crystal DiskMark. Today I added a second one to the motherboard - a 4TB Crucial P3 Plus (D:).

First I was copying from a SATA SSD to drive D. The copy speed would go up to nearly 500 MB/s but then it would drop down to 0. It would stay at 0 for a while, and then it would go up again, go back to 0, and repeat. It seemed like the D drive couldn't accept the data as fast as it should.

Then I ran the first test of Crystal DiskMark on both drives:

C: read: 7046 MB/s write 5500 MB/s
D: read 4978 MB/s write 94 MB/s - that's right - writing at ninety-four MB/S.

This must indicate a problem with writing to the D drive, right?
 

IDProG

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I got a new computer that came with a 2TB M.2 MVMe, and it has good benchmarks with Crystal DiskMark. Today I added a second one to the motherboard - a 4TB Crucial P3 Plus (D:).

First I was copying from a SATA SSD to drive D. The copy speed would go up to nearly 500 MB/s but then it would drop down to 0. It would stay at 0 for a while, and then it would go up again, go back to 0, and repeat. It seemed like the D drive couldn't accept the data as fast as it should.

Then I ran the first test of Crystal DiskMark on both drives:

C: read: 7046 MB/s write 5500 MB/s
D: read 4978 MB/s write 94 MB/s - that's right - writing at ninety-four MB/S.

This must indicate a problem with writing to the D drive, right?
Run CrystalDiskMark again, but screenshoot the Task Manager right before you run it test. What is the result?
 
I got a new computer that came with a 2TB M.2 MVMe, and it has good benchmarks with Crystal DiskMark. Today I added a second one to the motherboard - a 4TB Crucial P3 Plus (D:).

First I was copying from a SATA SSD to drive D. The copy speed would go up to nearly 500 MB/s but then it would drop down to 0. It would stay at 0 for a while, and then it would go up again, go back to 0, and repeat. It seemed like the D drive couldn't accept the data as fast as it should.

Then I ran the first test of Crystal DiskMark on both drives:

C: read: 7046 MB/s write 5500 MB/s
D: read 4978 MB/s write 94 MB/s - that's right - writing at ninety-four MB/S.

This must indicate a problem with writing to the D drive, right?
How is the drive mounted? Is there any heatsink or cooling pad? You could try this again while monitoring the drive's temperature.
 

USAFRet

Titan
Moderator
I got a new computer that came with a 2TB M.2 MVMe, and it has good benchmarks with Crystal DiskMark. Today I added a second one to the motherboard - a 4TB Crucial P3 Plus (D:).

First I was copying from a SATA SSD to drive D. The copy speed would go up to nearly 500 MB/s but then it would drop down to 0. It would stay at 0 for a while, and then it would go up again, go back to 0, and repeat. It seemed like the D drive couldn't accept the data as fast as it should.

Then I ran the first test of Crystal DiskMark on both drives:

C: read: 7046 MB/s write 5500 MB/s
D: read 4978 MB/s write 94 MB/s - that's right - writing at ninety-four MB/S.

This must indicate a problem with writing to the D drive, right?
What motherboard?

And copying from a SATA SSD to NVMe....speed is dictated by the slowest device in the chain.
There, the SATA SSD. It can only give the data to the NVMe at its speed, not what the NVMe can theoretically do.

Also, is write cache enabled on this drive?
It should be by default, but check anyway.
 
When you write a large amount of data to a ssd of any type, it will eventually overwhelm the capacity of the device.
When all of the initially free nand blocks are used up, the device reverts to a read/rewrite process.
Then, as those blocks are filled up the device needs to consolidate blocks to accept more data.
Yes, it may take hours to do a simple copy of 300gb.
 

Alan Alan

Prominent
Aug 9, 2022
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I got a new computer that came with a 2TB M.2 MVMe, and it has good benchmarks with Crystal DiskMark. Today I added a second one to the motherboard - a 4TB Crucial P3 Plus (D:).

First I was copying from a SATA SSD to drive D. The copy speed would go up to nearly 500 MB/s but then it would drop down to 0. It would stay at 0 for a while, and then it would go up again, go back to 0, and repeat. It seemed like the D drive couldn't accept the data as fast as it should.

Then I ran the first test of Crystal DiskMark on both drives:

C: read: 7046 MB/s write 5500 MB/s
D: read 4978 MB/s write 94 MB/s - that's right - writing at ninety-four MB/S.

This must indicate a problem with writing to the D drive, right?
It's possible the ssd's are overheating. They have a temperature sensor built in and when the temp increases their speed decreases.
 

GeorgiaOverdrive

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May 30, 2014
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Maybe. They were also acting like a buffer got filled up and it had to wait for the buffer to be written. These were some large files, and they would be fast, then drop to almost nothing, then get fast again, repeat.
 

Alan Alan

Prominent
Aug 9, 2022
218
9
595
Maybe. They were also acting like a buffer got filled up and it had to wait for the buffer to be written. These were some large files, and they would be fast, then drop to almost nothing, then get fast again, repeat.
I have a crucial ssd too. P3 plus, like yours, It always starts out fast then slows down. Mine was on a heat sync though, which is like talking apples and oranges. But I have read about the thermal limiting so that's real. It's just that your's might not have a heat sink on the chips. Today I dumped 35mps straight thru coming from a usb P3plus. It did not slow down and the P3 I wrote to wasn't heatsinked. If that helps...