"Drivers have been made to behave when using a bigger than 128KB maximum IO transfer size"

Wojciech Puchar wojtek at wojtek.tensor.gdynia.pl
Tue May 13 02:02:14 PDT 2014

> (x86_64/amd64) by default.
> I experimented for a while with the ahci driver; bigger values helped to
> increase linear (dd) performance by up to 20% with fast SSDs but it was unclear
> at the time if it would have improved regular filesystem operations.

it should when performing parallel reads/writes on multiple large files. 
prevents seeking. in freebsd it makes enormous difference.

> Even though all storage drivers compile fine with bigger MAXPHYS values it's
> also possible some will have issues at runtime.
> -- 
> Francois Tigeot

More information about the Users mailing list