nfssrv Module Parameters

This section describes NFS parameters for the nfssrv module.

nfssrv:nfs_portmon

Description

Controls some security checking that the NFS server attempts to do to enforce integrity on the part of its clients. The NFS server can check whether the source port from which a request was sent was a reserved port. A reserved port has a number less than 1024. For BSD-based systems, these ports are reserved for processes being run by root. This security checking can prevent users from writing their own RPC-based applications that defeat the access checking that the NFS client uses.

Data Type

Integer (32-bit)

Default

0 (security checking disabled)

Range

0 (security checking disabled) or 1 (security checking enabled)

Units

Boolean values

Dynamic?

Yes

Validation

None

When to Change

Use this parameter to prevent malicious users from gaining access to files by using the NFS server that they would not ordinarily have access to. However, the reserved port notion is not universally supported. Thus, the security aspects of the check are very weak. Also, not all NFS client implementations bind their transport endpoints to a port number in the reserved range. Thus, interoperability problems might result if the security checking is enabled.

Commitment Level

Unstable

nfssrv:rfs_write_async

Description

Controls the behavior of the NFS version 2 server when it processes WRITE requests. The NFS version 2 protocol mandates that all modified data and metadata associated with the WRITE request reside on stable storage before the server can respond to the client. NFS version 2 WRITE requests are limited to 8192 bytes of data. Thus, each WRITE request might cause multiple small writes to the storage subsystem. This can cause a performance problem.

One method to accelerate NFS version 2 WRITE requests is to take advantage of a client behavior. Clients tend to send WRITE requests in batches. The server can take advantage of this behavior by clustering together the different WRITE requests into a single request to the underlying file system. Thus, the data to be written to the storage subsystem can be written in fewer, larger requests. This method can significantly increase the throughput for WRITE requests.

Data Type

Integer (32-bit)

Default

1 (clustering enabled)

Range

0 (clustering disabled) or 1 (clustering enabled)

Units

Boolean values

Dynamic?

Yes

Validation

None

When to Change

Some very small NFS clients, particularly PC clients, might not batch WRITE requests. Thus, the behavior required from the clients might not exist. In addition, the clustering in the NFS version 2 server might just add overhead and slow down performance instead of increasing it.

Commitment Level

Unstable