what a difference an AHCI makes

Last week, I noticed how, whenever huge disk IO was taking place on my Quad-core – with 4Gb of RAM and 64bit Ubuntu – workstation at work, the whole desktop environment would pretty much grind to a halt.

SSH’ing in from a remote machine and using top, iotop and nethogs didn’t show anything particularly heart stopping going on either.

I googled around and found that this seemed to be a fairly common problem with any of the newer kernel releases.

One post in particular said that a person had fixed the problem by disabling the SATA disk controllers AHCI mode in the BIOS – switching it back to IDE.

Cool I thought – let’s have a go! Interestingly, the BIOS was already set to IDE. I decided I’d try enabling AHCI instead.

Wow – what a difference that made. I then remembered one of the other posts I came across that just said to switch the BIOS setting as that forces the OS to load a different disk controller driver.

It certainly did the trick – said work-beastie is now much faster and more responsive under load.

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