Linux FileSystem Internal Buffer size:

I know that Univ FileSystem stores all file data in the form of first few direct nodes followed by indirect nodes. But internally some systems implement where , a single block of 4096 isnt allocated alone a single block basis on physical drive, rather a large chunk of data is allocated and no. of blocks reside on it. This way they achieve efficieny in data read/write. This buffer contain blocks, can you anyone let me know the way to know that buffer size???? any ideas?

What is Fixed size disk block in Unix?

Which UNIX? Which FileSystem? Often the answer is: variable.