Samsung SSD EVO 840 120 GB Real copy speed so slow

[cloneuser]

Hello
I bought new SSD, SS SSD EVO 840 120GB, I used this drive only to install the Operation System (only 1 partition) and saved my data in old HDD.
(both drives use Sata 600)
I 've tested the speed by some softwares and it is awesome,

but real copy speed and random read are slow, this is the images:

I don't know why it is because this is first time I 've used a SSD
Please help me!

 

[Solandri]

That is normal. In your first pic, you see the row labeled 4k and 4k QD32? That's essentially what the random IOPS is measuring.

27 MB/s random 4k read and 51 MB/s random 4k write is about average for a SSD. And 85,000 and 100,000 IOPS (which correspond to the 4k 32 queue depth) is actually really good.

For comparison, most hard drives are around 0.8-1.5 MB/s random 4k read/writes, and 100-150 IOPS (yes, that is not a typo - a hundred to a hundred fifty). This is actually where SSDs get most of their speed. Their sequential read/writes are only about 3-4 times faster than a HDD. But their random 4k read/writes are typically about 30-50 times faster, and IOPS/4k with queue several hundred times faster. If you've ever had a virus scan kick in on a hard drive and the computer almost becomes unusable, this is why.

 

[cloneuser]

Thanks for replying, But I still don't understand, the sequential shown by software is ~ 500 MB/s but real copy is only 100 - 200 MB/s ?

 

[Solandri]

Thanks for replying, But I still don't understand, the sequential shown by software is ~ 500 MB/s but real copy is only 100 - 200 MB/s ?

Sequential reads are just like the name implies. A large, single file which needs to be read all at once.

Random 4k reads are a bunch of small (4k) files which are read. (Random 4k Queue Depth 32 means the drive is instructed to read 32 files at once.)

These are the two extremes when it comes to reading/writing data to a storage device (most sector or addressable memory cell sizes are 4k). The sequential scores are just a raw measure of how quickly the drive can read from its memory cells or off the platter. The random scores include latency caused by having to go through the file system to (for an SSD) look up individual memory addresses for each file or (for a HDD) reposition the heads and wait for the appropriate part of the disk to spin under the head. Consequently the random 4k reads are a lot slower than sequential reads.

When you copy a bunch of your personal files, the speed will fall in between these two extremes. Exactly where in between depends on the size of the files you're copying. If you're copying a bunch of 1 GB movies, then it'll be closer to the sequential speed. If you're copying a bunch of 10k text files and Word documents, then it'll be closer to the 4k random speed.

I assume you copied from one folder on the SSD to another folder on the same SSD? That'll roughly halve your speed since the drive has to spend half its time reading, half its time writing. The 137-158 MB/s you got is about what you'd expect in that case. It's slightly better than the 350 MB/s read + 161 MB/s write from the 4k QD32 score. (The actual number would be half the harmonic mean, or (2/(1/350 MB/s + 1/161 MB/s))/2 = 110 MB/s as as the expected slowest self-copy speed.)

 

[mad-max79]

Everything is fine. Your Evo has a so called Turbo Write Cache, which has 3 GB capacity, after this is filled up everything gets written directly on the SSD with 130-140 MB/s like you measured.