lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [thread-next>] [day] [month] [year] [list]
Date:	Thu, 11 Sep 2014 16:32:00 +0200
From:	Gionatan Danti <>
Subject: AHCI maximum transfer size

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:
The stackoverflow post seems to agree with this old article:

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.

Danti Gionatan
Supporto Tecnico
Assyoma S.r.l. -
email: -
GPG public key ID: FF5F32A8
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

Powered by blists - more mailing lists