Improving the Write Performance of an NFS Server
Chet Juszczak
Digital Equipment Corporation
Abstract
The Network File System (NFS) utilizes a stateless protocol between
clients and servers; the major advantage of this statelessness is that
NFS crash recovery is very easy. However, the protocol requires that
data modification operations such as write be fully committed to
stable storage before replying to the client. The cost of this is
significant in terms of response latency and server CPU and I/O
loading. This paper describes a write gathering technique that
exploits the fact that there are often several write requests for the
same file presented to the server at about the same time. With this
technique the data portions of these writes are combined and a single
metadata update is done that applies to them all. No replies are sent
to the client until after this metadata update has been fully
committed, thus the NFS crash recovery design is not violated. This
technique can be used in most NFS server implementations and requires
no client modifications.
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