Technocrat's Weblog

Sat, 02 Sep 2006

Performance tuning rsize and NFS

Abstract:

By adjusting the rsize option on NFS mounts is it possible to improve the read access time from a client perspective.

Problem

Reading large files, ISO images for example, from an NFS share can be slow. This impacts productivity.

Hypothesis

By adjusting the read buffer size of the mount command the read access time of the NFS mount should be improved.

Procedure

  1. Use an NFS client and server connected via a 100Mb Ethernet connection.
  2. Create a 2GB file on the shared directory on the server. 
            dd if=/dev/zero of=nfs_file bs=1024k count=2385

  3. From the client mount the NFS share using the desired rsize option. 
            mount -t nfs remote:/share /mount -o rsize=????

  4. Read the file from the mounted share while timing the results. Repeat this three times. 
            time dd if=/mnt/swan/nwatson/nfs_file of=/dev/null bs=16k

  5. Repeat this for each rsize option.

  6. Repeat this with the client and server connected via a 1Gb Ethernet connection.

Observations

Figure 1: Timing file transfers while altering rsize
NFS read performance with changing rsize

Conclusions

A rsize of 8192 offers the best performance using 100Mb Ethernet. Ethernet connects at 1Gb are fastest with an rsize of 32768 although not specifying the rsize was close second.

About this document ...

Performance tuning rsize and NFS

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The translation was initiated by Neil Watson on 2006-09-02

Neil Watson 2006-09-02