Re: AHCI maximum transfer size

[Gionatan Danti]

On 16/09/2014 10:56, Gionatan Danti wrote:
> > Hi all,
> > I searched the list and the internet for this question, but I did not
> > find a definitive answer.
> >
> > I wonder what is the maximum AHCI transfer size for kernel 2.6.32.x
> > Let me explain: using a command as "dd if=/dev/zero of=/dev/sda bs=2M" I
> > can see, via iostat, that request-size is at 2M (as expected). However
> > it seems to me that the effective transfer size is way lower: disabling
> > writeback cache on the target disk, I see very low performance even for
> > big-chunk transfers.
> >
> > Googling, I found this post on stackoverflow stating that maximum
> > observerd AHCI transfer size (with a SATA protocol analyzer) is 128KB:
> > http://stackoverflow.com/questions/24053662/how-to-enlarge-sata-transfer-size-in-linux-ahci-driver.
> >
> >
> > The stackoverflow post seems to agree with this old LWN.net article:
> > http://lwn.net/Articles/77981/
> >
> > Anyone has any idea of how to find (and eventually change) the used AHCI
> > transfer size without touching the code?
> >
> > NOTE: please CC me directly.
> > Regards.
>
> Hi all,
> any idea on the subject?
>
> Regards.

Hi guys,
anyone with a suggestion?

Thank you.

--
Danti Gionatan
Supporto Tecnico
Assyoma S.r.l. - www.assyoma.it
email: g.danti@xxxxxxxxxx - info@xxxxxxxxxx
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