why nfs is so slow?

Tue Dec 11 04:29:57 PST 2007

On Tue, 11 Dec 2007, Wojciech Puchar wrote:

> i'm getting about 6MB/s with NFS (100Mbit cross-connect ethernet), while over 
> 9.5 by FTP.
>
> nfs is set to work over TCP.

To my mind, this is because NFS is stateless because of being designed to 
share filesystem on a whole local network. Thus, every remote procedure 
call (the basic NFS operation) is self contained. Thus, every single read 
request causes the server to open the file, to read the number of bytes 
requested, and to close the file.

If you compare this to a typical peer-to-peer ftp session, the overhead is 
obvious. On the other hand, ftp is a very special application.

Best regards

Konrad Heuer
GWDG, Am Fassberg, 37077 Goettingen, Germany, kheuer2 at gwdg.de