AHCI slower than IDE :-P

Not a request for help, just something I wanted to share. I'm sure there's one or two opinions waiting to be heard. :)

So, I switched my SATA controller over to AHCI from IDE, since I have a new OCZ Vertex Plus 60GB SSD...enabled the registry setting for the MSAHCI driver before rebooting and everything is beautiful. Just as before.

Just as before? Not quite. LOL. See for yourself...


ATTO benchmark results - IDE mode




ATTO benchmark results - AHCI mode





In AHCI, performance actually drops across the board, just slightly - except that reading large blocks gets a few MB/sec faster starting with 128KB blocks.

Hmm. I was expecting a tiny bit more. But now that I'm on AHCI I'll leave it, even if there's no actual advantage it's nice to know NCQ is enabled. :)

No dependency? I understand that ATTO is one of the best disk benchmarks for SSDs because it can queue I/O requests and put NCQ to work that way. I do realize, though, that NCQ would have more of an effect with harddisks and their comparatively huge access times.

What you're saying suggests there would be no difference between IDE and AHCI, period. I'm sure some people would beg to differ...

And I'm well aware of fluctuations from test to test, but the conclusion remains that in my particular case, AHCI brought very little advantage.

Do you think something was wrong with my testing methodology? Or have suggestions for other benchmark apps?

FWIW
I had called Gigabyte several months ago about changing from IDE to AHCI. The tech told me they (Gigabyte) had found little speed difference between the two.

logicearth said:

There is no performance difference to IDE or AHCI because they are only communication protocols. The actual physical SATA connection is what determines the speed. Not whether you are using IDE or AHCI. IDE and AHCI will preform the same because the SATA connection is the same speed regardless.

When you put it like that, it makes perfect sense of course. Besides, I didn't expect any miracles - though I would have thought that very-small-block writes would have sped up a little, but that does differ from system to system.

Curious, though, why so many then claim that "AHCI is faster than IDE." But this is exactly why I shared my findings to invite opinions. I have no problem at all with my numbers. :)

ATTO is one of the worst benchmarks. It uses fully compressible data (all zeros). It also does not do many threaded small reads and writes (i.e. 64 thread 4k random reads.writes), where AHCI will perform much better than IDE

Arguably the best synthetic benchmark is AS_SSD.

Besides, from what I see of your posting, it looks like AHCI is slightly better

Hmm.

I'll try AS-SSD again, then, but I had the impression ATTO was widely regarded as the best. Ahwell :)

Not sure what compressible data would have to do with anything, unless you're thinking Sandforce controllers and their built-in compression. My SSD uses an Indilink Martini controller.

Corazon said:

Hmm.

I'll try AS-SSD again, then, but I had the impression ATTO was widely regarded as the best. Ahwell :)

Not sure what compressible data would have to do with anything, unless you're thinking Sandforce controllers and their built-in compression. My SSD uses an Indilink Martini controller.

Only by vendors whose drives do compression so their rates look higher LOL