Messages in this thread | | | Date | Wed, 4 Feb 2009 00:40:03 +0100 | From | "J.A. Magallón" <> | Subject | Re: SSD and IO schedulers |
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On Fri, 30 Jan 2009 22:55:47 +0100, Lorenzo Allegrucci <l.allegrucci@gmail.com> wrote:
> Hi, I was wondering how IO schedulers such as as-iosched, deadline and > cfq behave on SSD > (that have virtually no seek time), from a theoretical point of view. > How do they affect > performance on these devices? > I heard that the noop scheduler is often chosen by owners of EeePcs > (with a SSD unit).
I'm beginning to think this is a _very_ bad idea. I have an AspireOne A110 (512MB, 8GB SSD). This is 'not the best SSD in the world', to say something. I had been booting with elevator=noop, because of all those advices found along many blogs.
The fact is that the system behaved well, except when I was doing an 'urpmi --auto-update' (I use Mandriva). The bulk of rpm work rendered the box unusable. 5-10 seconds stalls and so on.
After reading this, I killed the elevator option from grub, the system uses the default cfq scheduler, and things are much smoother and the laptop is perfectly usable while doing an update. I think even rpm itself works faster.
Perhaps the reason is that, as the SSD is not so good, it behaves more like a rotational drive ;).
> They report superior performance by using this (quite simple) scheduler. > Are there any scientific benchmarks around? >
A couple questions: - Apart from noop, which scheduler do you think is the best for SSDs ? - I'm running 2.6.28.2. Does it have the 'SSD detector' in libata ? How can I verify it ?
TIA
-- J.A. Magallon <jamagallon()ono!com> \ Software is like sex: \ It's better when it's free Mandriva Linux release 2009.1 (Cooker) for x86_64 Linux 2.6.28.2-desktop-1mnb (gcc 4.3.2 (GCC) #1 Wed Jan
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