I got a new SSD, Crucial BX200, 480 GB. It is plugged into a sata 3 port. I installed Linux Mint 17.3 Cinnamon 64 Bit on the ssd (using full disk encryption)

If I run bonnie++ to do a benchmark, I get something like 90 mb/s writing, 500 in mb/s reading. Using dd if=/dev/zero of=file bs=1M count=10000 gets me something like 110 mb/s.

This is to slow. Sata 3 and the disk should give me something around 500 mb/s.

Also I noticed that if I run dd, my system gets really laggy. I tried everthing I could think of ... using discard and barrier=0 in fstab. I reinstalled without encryption. I made sure that ahci is running. Nothing works.

Interestingly, when I go to Windows 7 and format the drive with NTFS, CrystalDiskMark gives me around 470 mb/s as a result.

So ... bug in Linux? Any ideas? Thx.

  • Is the trim option active?
    – DrNoone
    Feb 5, 2016 at 21:20
  • If you are reading 500 mb/sec and writing 110 mb/sec and you are expecting to write 500 mb/sec where exactly is the slow down ?
    – Ramhound
    Feb 5, 2016 at 21:33
  • 1
    Sounds like a bug in the benchmark: ( pcworld.com/article/3000913/storage/… ) calls it a dual drive with a small faster "cache" and a slower larger storage portion that writes at 80MB. They have graphs that show write speed fall off a cliff at the cache size
    – Yorik
    Feb 5, 2016 at 22:38
  • What kind of full disk encryption are you using? What kind of SATA port is the disk plugged into? What filesystem are you using? Feb 5, 2016 at 22:43
  • 1
    the BX200 is the worst SSD you could buy for writing data. after the cache is filled, the write speed is at HDD level. Feb 6, 2016 at 7:55

1 Answer 1


The BX200 has slow TLC NAND, with a 6GB of faster write cache on the 480GB model. After the cache is exhausted, it will write at the actual speed of the TLC NAND. I can think of two possibilities that could be affecting your benchmark:

  1. Bonnie++ is writing more than the 6GB, after which it will continue to write at the lower throughput. Then bonnie++ is likely using the lower value or average, as it's result.

  2. Something else may be already writing to the disk, and the cache is full, causing the cache to become exhausted earlier.

Try running dd with less than 6GB of data written.

Crystal DiskMark defaults to only 1GB on test, so you could try upping that to 8 or 16 for comparison.

  • oh crap ... that seems to be the case. If use dd with filesizes below 6 GB, it gives something between 200 and 400 mb/s, probably depending on what the system is doing while the test runs. Above 6gb it goes down to about 100 mb/s. Thats what I get for buying it just because its cheap. Thx!
    – Pythoneer
    Feb 6, 2016 at 23:56
  • @Pythoneer before buying a SSD you should always look for tests in the Internet. And they showed this slowdown. Feb 8, 2016 at 16:45

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