Very slow write access to SSD disks on some Asus P8Z77 motherboards

Posted by lenik on Ask Ubuntu See other posts from Ask Ubuntu or by lenik
Published on 2014-08-23T03:03:26Z Indexed on 2014/08/23 4:28 UTC
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I have Asus P8Z77-V LK motherboard, that ran Mint 13 (based on Ubuntu 12.04) just perfectly, but recently I've tried to install Mint 17 and noticed abysmal write performance. Write speed on SSD disk was about 1.5MB/sec, when it's supposed to be in 150-250MB/sec range. For write testing I've used dd if=/dev/zero of=/dev/sda bs=10M count=10 while booted up from LiveCD.

I have also tested the read speed with hdparm -tT /dev/sda and got about 440MB/sec -- that's normal. I can tell, the read performance has not degraded at all and is not an issue here.

Since I had a few different SSD disks and few motherboards, I've tested and tested and here are results:

  • Asus P8H77 works fine with Mint13, has very slow write speed starting from Mint14.
  • Asus P8Z77-V LK works with Mint13, has very slow write speed starting from Mint14.
  • Asus P8Z77-V PRO works with Mint13, and works just fine with Mint14, 15, 16 and 17.

The only difference between "PRO" version and others is that it has extra SATA controller onboard (in addition to the Z77 chipset SATA controller) providing extra 2 SATA ports. SSD disks work fine with "PRO" version when connected to the native SATA ports as well as to the ports provided by extra SATA controller, so this does not look like a hardware issue.

As far as I can tell, there's something changed in the kernel while going from 3.2 to 3.5, that affects the detection of onboard SATA controller for Asus P8*77 motherboards, that screws up the write speed for SSD drives.

Could anyone shed some light on how to fix this issue or, possibly, give a pointer to a more suitable place to ask this question?

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