Hi,

I have SATA disk connected to my system running centos, i am looking for the disk i/o function which is responsible to do the read/write on disk, would somebody point me?

Thanks,
Saurin

AHCI is used by kernel to perform read and write operation. Could you be more specific as to what exactly you are looking for? Are you looking for specific parameters that can be tuned?

I Want to process the data just before it is written to disk. also wants to process the data immediately after reading from disk.

That is how it is done. So am not quite sure what exactly you are looking for? For example: If an application given task to process the data it will contact the kernel, kernel then load that process in CPU, if data is there on cache or RAM it will pick it up else will go to disk for getting the relevant data. Once data is process it will be written to the disk. Vice-versa happens when you talk about reading from the disk.

If you are talking about parameters for performing immediate sync which are responsible for writing the data immediately to the disk then that is something different.

I am interested to know the function responsible in kernel which writes the chunk of data to the disk. looks like it is not strait forward to find that function.

Ok it is the application that writes to the disk with the help of the kernel. When application has to write any data to the disk post processing (already explained in my previous post) it will tell the kernel that I want to write this stuff to the disk. Kernel will then provide VFS (virtual file system because application doesn't care about the file system you are running on) to the application for data writing which in turn in the backend with the help of kernel writes to the disk.

May be my question is not clear. Let me ask this way, In a block driver after the I/O scheduler which function is responsible for writing into disk?

Now it is quite clear. Basically you are looking for which function is invoked by ahci module (block driver) which helps the kernel to write. Have a look at this wiki and read the POSIX section of it: http://en.wikipedia.org/wiki/Write_(system_call) .