In some of my previous posts, I spent some time attempting to squeeze out the best NFS performance as possible from OpenBSD. This time, I wanted to run a similar test, but on Linux and see if the same findings were applicable.

I found the results rather interesting, as they show that Linux is capable of faster transfer speeds than OpenBSD, with much less work. Of course, this doesn’t make me dislike OpenBSD any less (obviously), as the OS is still capable of fast transfers, and I am not building any supercomputers at my home.

I know there are plenty of articles out there which go into great detail on achieving the best possible NFS performance. However, most of the articles only highlighted possible settings to use, but none of them offered a way for anyone to test those settings. The script at the bottom of this article should enable admins to automate the process of finding the proper NFS values for their servers.

First off, I did some research and have tweaked my original NFS testing script used in earlier articles to do away with rsync, and switch to using dd with special flags to bypass the RAM cache Linux uses. This is done to test the raw transfer speeds, and not have results skewed by buffering.

Also, RHEL7/CentOS7 recommends to use TCP, and not UDP, as read here.

For this reason, I am only running my tests using TCP. Also, when I did do some testing using UDP on the CentOS server, I saw massive speed degradation, that was not seen when using TCP.

Also, the script has been modified to run read, as well as write tests.

Top 30 Read Results:

Direction   Sync        Protocol    Mount   Buffer      Transfer Size       Transfer Time       Transfer Speed
read        sync        tcp         soft    131072      4096                36.5489             118MB/s
read        sync        tcp         soft    131072      2048                18.2744             118MB/s
read        sync        tcp         soft    131072      1024                9.13749             118MB/s
read        sync        tcp         hard    131072      4096                36.5475             118MB/s
read        sync        tcp         hard    131072      2048                18.2746             118MB/s
read        sync        tcp         hard    131072      1024                9.13775             118MB/s
read        async       tcp         soft    131072      4096                36.5473             118MB/s
read        async       tcp         soft    131072      2048                18.2741             118MB/s
read        async       tcp         soft    131072      1024                9.13767             118MB/s
read        async       tcp         hard    131072      4096                36.5479             118MB/s
read        async       tcp         hard    131072      2048                18.2747             118MB/s
read        async       tcp         hard    131072      1024                9.13783             118MB/s
read        sync        tcp         soft    65536       4096                36.6083             117MB/s
read        sync        tcp         soft    65536       2048                18.3038             117MB/s
read        sync        tcp         soft    65536       1024                9.15332             117MB/s
read        sync        tcp         soft    32768       4096                36.6747             117MB/s
read        sync        tcp         soft    32768       2048                18.3372             117MB/s
read        sync        tcp         soft    32768       1024                9.17016             117MB/s
read        sync        tcp         hard    65536       4096                36.6055             117MB/s
read        sync        tcp         hard    65536       2048                18.3032             117MB/s
read        sync        tcp         hard    65536       1024                9.15207             117MB/s
read        sync        tcp         hard    32768       4096                36.6751             117MB/s
read        sync        tcp         hard    32768       1024                9.16981             117MB/s
read        async       tcp         soft    65536       4096                36.6052             117MB/s
read        async       tcp         soft    65536       2048                18.3035             117MB/s
read        async       tcp         soft    65536       1024                9.15207             117MB/s
read        async       tcp         soft    32768       4096                36.6767             117MB/s
read        async       tcp         soft    32768       2048                18.3374             117MB/s
read        async       tcp         soft    32768       1024                9.16966             117MB/s
read        async       tcp         hard    65536       4096                36.6047             117MB/s

Top 30 Write Results:

Direction   Sync        Protocol    Mount   Buffer      Transfer Size       Transfer Time       Transfer Speed
write       sync        tcp         soft    65536       1024                12.7614             84.1MB/s
write       sync        tcp         soft    32768       4096                51.0877             84.1MB/s
write       sync        tcp         soft    32768       2048                25.5335             84.1MB/s
write       sync        tcp         soft    32768       1024                12.7988             83.9MB/s
write       sync        tcp         soft    131072      2048                25.6036             83.9MB/s
write       async       tcp         soft    32768       2048                25.5911             83.9MB/s
write       async       tcp         soft    32768       1024                12.8041             83.9MB/s
write       async       tcp         hard    65536       2048                25.5911             83.9MB/s
write       async       tcp         hard    32768       2048                25.5999             83.9MB/s
write       sync        tcp         hard    65536       2048                25.6387             83.8MB/s
write       async       tcp         soft    32768       4096                51.2749             83.8MB/s
write       async       tcp         hard    32768       4096                51.2585             83.8MB/s
write       sync        tcp         soft    65536       2048                25.6436             83.7MB/s
write       sync        tcp         hard    65536       4096                51.3207             83.7MB/s
write       async       tcp         hard    65536       1024                12.8344             83.7MB/s
write       async       tcp         hard    65536       4096                51.3744             83.6MB/s
write       sync        tcp         soft    65536       4096                51.4253             83.5MB/s
write       sync        tcp         hard    65536       1024                12.8609             83.5MB/s
write       sync        tcp         hard    32768       4096                51.4328             83.5MB/s
write       async       tcp         hard    32768       1024                12.8662             83.5MB/s
write       sync        tcp         hard    32768       1024                12.8715             83.4MB/s
write       sync        tcp         hard    131072      2048                25.7637             83.4MB/s
write       async       tcp         soft    131072      4096                51.5276             83.4MB/s
write       async       tcp         soft    65536       1024                12.8935             83.3MB/s
write       sync        tcp         hard    131072      1024                12.9163             83.1MB/s
write       async       tcp         soft    65536       2048                25.8834             83.0MB/s
write       async       tcp         hard    131072      1024                12.9441             83.0MB/s
write       async       tcp         soft    65536       4096                51.8221             82.9MB/s
write       async       tcp         soft    131072      1024                12.9866             82.7MB/s
write       async       tcp         hard    131072      2048                26.0415             82.5MB/s


Interpretations

This go-around, I ran the results through Minitab, which was able to generate these plots for further analysis, and yes, synchronous is misspelled:

Linux NFS Interactive Plot

My interpretation of this plot is that Linux is overall very good at transferring data over NFSv3 with a majority of settings. As long as the buffer size was larger than 16384, the transfer speeds were pretty consistent for both reading and writing.

Linux NFS Main Effects Plot

My comments for this plot echo what was said regarding the previous plot. A majority of settings have little affect on the speed on NFS. It does look here that async and hard settings yielded slightly higher results, but barely.


Here is the script that was used to generate these results:

#!/bin/bash

# 1. sync vs async
# 2. TCP vs UDP, ignoring since UDP sucks in my tests on linux
# 3. soft vs hard
# 3. r/w size: 16384 32768 65536 131072

######################
### SET THESE VARS ###
######################

# Log location
log=/tmp/nfstest.log

# NFS share to mount
share=<server>:/tank0/nfs/share

# Mount location
mnt_dir=/data

########################
### script continues ###
########################

# Standard nfs options
standard='nfsvers=3,'

data[0]=1024    # 1G
data[1]=2048    # 2G
data[2]=4096    # 4G

# Declare starting point in log
echo "protocol,synchronous,mount,buffer,data size,direction,transfer time,transfer speed" >> $log

for protocol in tcp udp
do
    echo "$(date) - Using $protocol"
    protocol=${protocol},

    for synchronous in async sync
    do
        echo "$(date) - Using $synchronous"
        synchronous=${synchronous},

        for mount in hard soft
        do
            echo "$(date) - Using $mount"
            mount=${mount},

            for size in 16384 32768 65536 131072
            do
                echo "$(date) - Using a $size byte r/w buffer"

                # Unmount share
                echo "$(date) - Remounting share"
                sudo umount $mnt_dir >/dev/null 2>&1
                sudo mount.nfs -o ${synchronous}${protocol}${mount}${standard}rsize=$size,wsize=$size $share $mnt_dir

                for e in 0 1 2
                do
                    echo "$(date) - Using ${data[$e]}MB"

                    for direction in write read
                    do
                        # Transfer file
                        if [[ $direction == "write" ]]; then
                            echo -n "$(date) - Writing data: "
                            # Write the direct with no caching
                            action=$(dd if=/dev/zero of=${mnt_dir}/zeros.file bs=1M count=${data[$e]} oflag=direct 2>&1)    
                            # Write while utilizing cache 
                            # action=$(dd if=/dev/zero of=${mnt_dir}/zeros.file bs=1M count=${data[$e]} 2>&1)

                            # echo transfer info
                            action_thr=$(echo $action | awk '{print $14$15}')
                            action_time=$(echo $action | awk '{print $12}')
                            echo "$action_thr"

                        else
                            echo -n "$(date) - Reading data: "
                            action=$(dd if=${mnt_dir}/zeros.file of=/dev/null bs=1M 2>&1) 

                            # echo transfer info
                            action_thr=$(echo $action | awk '{print $14$15}')
                            action_time=$(echo $action | awk '{print $12}')
                            echo "$action_thr"
                        fi

                        data_time=$action_time                        
                        data_trans=$action_thr

                        # Sync
                        echo "$(date) - syncing"
                        sync

                        # Save transfer info to log
                        echo "${direction},${synchronous}${protocol}${mount}$size,${data[$e]},${data_time},${data_trans}" >> $log
                    done
                done

                # Unmount share and get duration
                echo "$(date) - Unmounting share"
                umount_time=$({ time -p sudo umount $mnt_dir;} 2>&1 | grep real | awk '{print $2}')
            done
        done
    done
done


Server Notes:

NFS Server: OS: FreeBSD 12.0
CPU: Intel® Xeon® CPU E3-1275 v6 @ 3.80GHz (3792.20-MHz K8-class CPU)
Network: 4 1Gbps igb NICs bonded using LACP

NFS Client OS: CentOS7
CPU: Intel® Core™ i3-6100 CPU @ 3.70GHz, 3701.39 MHz, 06-5e-03
Network: 4 1Gbps NICs bonded using LACP

Has been tested on Centos7