3.1.2 Matrix Server Command Reference

Chapter 1: Matrix Server Commands 27

12+$4*2... I/O statistics in quads, or groups of four numbers. (The number of

quads appears in field 6, “Number of I/O sizes”). Each quad consists of the

following fields for each I/O size:

• Minimum latency

• Maximum latency

• Count of I/Os

• Total latency for all I/Os

The minimum and maximum latency are reset every interval. Latencies are in

microseconds.

mxnlmconfig – enable or disable NLM

Synopsis

/opt/polyserve/bin/mxnlmconfig -q|-e|-d

Description

This command is provided by the MxFS-Linux Solution Pack. NLM is the

locking protocol used by NFS. By default, it is disabled in MxFS-Linux. If

necessary, NLM can be enabled; however, you should be aware of the

following caveat:

• File locks granted by the NFS server are cluster-coherent. When a failover

occurs, the locks are released by the original server and the client

automatically reclaims them on the new server (the backup node).

However, during the period after the lock is released, another client or

application may compete for and win the lock. Some NFS clients will

return an error to the client applications if the lock cannot be reclaimed.

Other clients (for example, the Linux 2.6 NFS client) will not return any

error. If no error is returned by the client, the application may proceed

under the false assumption that the lock has been granted. Data

corruption may be the result.

To prevent this situation, locking should be enabled only if your clients are

partitioned so that all clients needing a particular lock are using the same

Virtual NFS Service IP address. If a failover occurs, all of the clients will