NFS and Shared Folder creation between servers

Install NFS on all your servers

yum install nfs-utils -y
service rpcbind start
service nfs start

service autofs restart

NFS server side

Then, in your "NFS server", create the shared folder (aka the folder to be shared)

mkdir /home/mich/SHARED_FOLDER
chmod a+w /home/mich/SHARED_FOLDER

Define the mount folder:

vi /etc/exports /home/mich/SHARED_FOLDER 192.168.1.0/24(rw,sync,no_root_squash,no_all_squash)

where the  192.168.1.0/24 is the IP range of the servers authorized to access this mounted folders

In order to make the export change effective, type:

exportfs -a

then, do not forget to start nfs

/etc/init.d/nfs start

or even to start it automatically in startup:
for ex:

cat /etc/rc.d/rc.local 

#!/bin/sh
#
# This script will be executed *after* all the other init scripts.
# You can put your own initialization stuff in here if you don't
# want to do the full Sys V style init stuff.
depmod -a
modprobe acpiphp
if [ -f /etc/rc.firstboot ]
then
        /etc/rc.firstboot | tee /var/log/firstboot.log
        cp /etc/rc.firstboot /usr/local/etc/
        rm /etc/rc.firstboot
        reboot
fi
touch /var/lock/subsys/local
/etc/init.d/nfs start

NFS CLIENT side

Then, on each client side, that want to use this mount :

mkdir /nfs/shared
mount -t nfs 192.168.20.11:/home/mich/SHARED_FOLDER/ /nfs/shared/

where 192.168.20.11 is the IP of the NFS server that you've configured in the previous paragraph

or do it automatically after startup:

vi /etc/fstab

add something like:

192.168.20.11:/home/mich/SHARED_FOLDER/ /nfs/shared/  nfs rsize=8192,wsize=8192,timeo=14,intr

if you want to test it without reboot your machine, do simply

mount -a

All those instructions were freely and quite fully inspired from this link:

https://ostechnix.wordpress.com/2013/12/15/setup-nfs-server-in-centos-rhel-scientific-linux-6-3-step-by-step/

Network Connection

In order to understand the spec of the network card being used by your server:

lspci | grep -i net

Here, as example of the status on my job's cloud : 

ro -a -o . -h els2 -s shared -irc %/ lspci | grep -i net
[ virginia / svpr-els204 ] - 03:00.0 Ethernet controller: Broadcom Corporation NetXtreme BCM5719 Gigabit Ethernet PCIe (rev 01)        <<== which means 1 GB only
[ virginia / svpr-els204 ] - 03:00.1 Ethernet controller: Broadcom Corporation NetXtreme BCM5719 Gigabit Ethernet PCIe (rev 01)
[ virginia / svpr-els204 ] - 03:00.2 Ethernet controller: Broadcom Corporation NetXtreme BCM5719 Gigabit Ethernet PCIe (rev 01)
[ virginia / svpr-els204 ] - 03:00.3 Ethernet controller: Broadcom Corporation NetXtreme BCM5719 Gigabit Ethernet PCIe (rev 01)
[ virginia / svpr-els205 ] - 03:00.0 Ethernet controller: Broadcom Corporation NetXtreme BCM5719 Gigabit Ethernet PCIe (rev 01)
[ virginia / svpr-els205 ] - 03:00.1 Ethernet controller: Broadcom Corporation NetXtreme BCM5719 Gigabit Ethernet PCIe (rev 01)
[ virginia / svpr-els205 ] - 03:00.2 Ethernet controller: Broadcom Corporation NetXtreme BCM5719 Gigabit Ethernet PCIe (rev 01)
[ virginia / svpr-els205 ] - 03:00.3 Ethernet controller: Broadcom Corporation NetXtreme BCM5719 Gigabit Ethernet PCIe (rev 01)
[ virginia / svpr-els206 ] - 03:00.0 Ethernet controller: Broadcom Corporation NetXtreme BCM5719 Gigabit Ethernet PCIe (rev 01)
[ virginia / svpr-els206 ] - 03:00.1 Ethernet controller: Broadcom Corporation NetXtreme BCM5719 Gigabit Ethernet PCIe (rev 01)
[ virginia / svpr-els206 ] - 03:00.2 Ethernet controller: Broadcom Corporation NetXtreme BCM5719 Gigabit Ethernet PCIe (rev 01)
[ virginia / svpr-els206 ] - 03:00.3 Ethernet controller: Broadcom Corporation NetXtreme BCM5719 Gigabit Ethernet PCIe (rev 01)
[ virginia / svpr-els207 ] - 04:00.0 Ethernet controller: Emulex Corporation OneConnect 10Gb NIC (be3) (rev 01)             <<== this means the card is 10Gb/sec 
[ virginia / svpr-els207 ] - 04:00.1 Ethernet controller: Emulex Corporation OneConnect 10Gb NIC (be3) (rev 01)
[ virginia / svpr-els208 ] - 04:00.0 Ethernet controller: Emulex Corporation OneConnect 10Gb NIC (be3) (rev 01)
[ virginia / svpr-els208 ] - 04:00.1 Ethernet controller: Emulex Corporation OneConnect 10Gb NIC (be3) (rev 01)
[ virginia / svpr-els209 ] - 04:00.0 Ethernet controller: Emulex Corporation OneConnect 10Gb NIC (be3) (rev 01)
[ virginia / svpr-els209 ] - 04:00.1 Ethernet controller: Emulex Corporation OneConnect 10Gb NIC (be3) (rev 01)
[ virginia / svpr-els21 ] - 04:00.0 Ethernet controller: Emulex Corporation OneConnect 10Gb NIC (be3) (rev 01)
[ virginia / svpr-els21 ] - 04:00.1 Ethernet controller: Emulex Corporation OneConnect 10Gb NIC (be3) (rev 01)
[ virginia / svpr-els210 ] - 04:00.0 Ethernet controller: Emulex Corporation OneConnect 10Gb NIC (be3) (rev 01)
[ virginia / svpr-els210 ] - 04:00.1 Ethernet controller: Emulex Corporation OneConnect 10Gb NIC (be3) (rev 01)
[ virginia / svpr-els211 ] - 04:00.0 Ethernet controller: Emulex Corporation OneConnect 10Gb NIC (be3) (rev 01)
[ virginia / svpr-els211 ] - 04:00.1 Ethernet controller: Emulex Corporation OneConnect 10Gb NIC (be3) (rev 01)
[ virginia / svpr-els212 ] - 04:00.0 Ethernet controller: Emulex Corporation OneConnect 10Gb NIC (be3) (rev 01)
[ virginia / svpr-els212 ] - 04:00.1 Ethernet controller: Emulex Corporation OneConnect 10Gb NIC (be3) (rev 01)
[ virginia / svpr-els22 ] - 04:00.0 Ethernet controller: Emulex Corporation OneConnect 10Gb NIC (be3) (rev 01)
[ virginia / svpr-els22 ] - 04:00.1 Ethernet controller: Emulex Corporation OneConnect 10Gb NIC (be3) (rev 01)

In addition, in order to understand the SWAP memory usage :

free -g 

 free -g             total       used       free     shared    buffers     cachedMem:           125        110         15          0          3         67-/+ buffers/cache:         39         86Swap:          128          0        128

==> Means that the OS has about 67+15 GB available

If you don't want to use swap (it may slow your server/application etc) 

• swapoff -a   ==> do never use swap
• sysctl vm.swappiness=0   ==> use swap only if you don't have any more choice
• sysctl vm.swappiness=60   ==> use swap only if you reach more than 60% of the memory
• swapon -a ==> enable usage of SWAP, according to the swappiness value 
•  sysctl -a |grep swap  : to understand what is the % policy value.

Using top, you can have the following:

Mem:  132119828k total, 131341592k used,   778236k free,  3505520k buffers

Swap: 134365176k total,    88752k used, 134276424k free, 105451036k cached  <<== this is the FULL RAM available

More info regarding swap can be found: 

http://askubuntu.com/questions/103915/how-do-i-configure-swappiness