14.3. Example Configurations

In this section we go through a few examples of how to set up storage to work properly on a few types of NFS and iSCSI storage systems.

14.3.1. Linux NFS on Local Disks and DAS

This section describes how to configure an NFS export on a standard Linux installation. The exact commands might vary depending on the operating system version.

Install the RHEL/CentOS distribution on the storage server.
If the root volume is more than 2 TB in size, create a smaller boot volume to install RHEL/CentOS. A root volume of 20 GB should be sufficient.
After the system is installed, create a directory called /export. This can each be a directory in the root partition itself or a mount point for a large disk volume.
If you have more than 16TB of storage on one host, create multiple EXT3 file systems and multiple NFS exports. Individual EXT3 file systems cannot exceed 16TB.
After /export directory is created, run the following command to configure it as an NFS export.
```
# echo "/export <CIDR>(rw,async,no_root_squash,no_subtree_check)" >> /etc/exports
```
Adjust the above command to suit your deployment needs.
- Limiting NFS export. It is highly recommended that you limit the NFS export to a particular subnet by specifying a subnet mask (e.g.,”192.168.1.0/24”). By allowing access from only within the expected cluster, you avoid having non-pool member mount the storage. The limit you place must include the management network(s) and the storage network(s). If the two are the same network then one CIDR is sufficient. If you have a separate storage network you must provide separate CIDR’s for both or one CIDR that is broad enough to span both.
  The following is an example with separate CIDRs:
```
/export 192.168.1.0/24(rw,async,no_root_squash,no_subtree_check) 10.50.1.0/24(rw,async,no_root_squash,no_subtree_check)
```
- Removing the async flag. The async flag improves performance by allowing the NFS server to respond before writes are committed to the disk. Remove the async flag in your mission critical production deployment.
Run the following command to enable NFS service.
```
# chkconfig nfs on
```

Edit the /etc/sysconfig/nfs file and uncomment the following lines.

LOCKD_TCPPORT=32803
LOCKD_UDPPORT=32769
MOUNTD_PORT=892
RQUOTAD_PORT=875
STATD_PORT=662
STATD_OUTGOING_PORT=2020

Edit the /etc/sysconfig/iptables file and add the following lines at the beginning of the INPUT chain.

-A INPUT -m state --state NEW -p udp --dport 111 -j ACCEPT
-A INPUT -m state --state NEW -p tcp --dport 111 -j ACCEPT
-A INPUT -m state --state NEW -p tcp --dport 2049 -j ACCEPT
-A INPUT -m state --state NEW -p tcp --dport 32803 -j ACCEPT
-A INPUT -m state --state NEW -p udp --dport 32769 -j ACCEPT
-A INPUT -m state --state NEW -p tcp --dport 892 -j ACCEPT
-A INPUT -m state --state NEW -p udp --dport 892 -j ACCEPT
-A INPUT -m state --state NEW -p tcp --dport 875 -j ACCEPT
-A INPUT -m state --state NEW -p udp --dport 875 -j ACCEPT
-A INPUT -m state --state NEW -p tcp --dport 662 -j ACCEPT
-A INPUT -m state --state NEW -p udp --dport 662 -j ACCEPT

Reboot the server.
An NFS share called /export is now set up.

Note

When copying and pasting a command, be sure the command has pasted as a single line before executing. Some document viewers may introduce unwanted line breaks in copied text.

14.3.2. Linux NFS on iSCSI

Use the following steps to set up a Linux NFS server export on an iSCSI volume. These steps apply to RHEL/CentOS 5 distributions.

Install iscsiadm.

# yum install iscsi-initiator-utils
# service iscsi start
# chkconfig --add iscsi
# chkconfig iscsi on

Discover the iSCSI target.

# iscsiadm -m discovery -t st -p <iSCSI Server IP address>:3260

For example:

# iscsiadm -m discovery -t st -p 172.23.10.240:3260
          172.23.10.240:3260,1 iqn.2001-05.com.equallogic:0-8a0906-83bcb3401-16e0002fd0a46f3d-rhel5-test

# iscsiadm -m node -T <Complete Target Name> -l -p <Group IP>:3260

For example:

# iscsiadm -m node -l -T iqn.2001-05.com.equallogic:83bcb3401-16e0002fd0a46f3d-rhel5-test -p 172.23.10.240:3260

Discover the SCSI disk. For example:

# iscsiadm -m session -P3 | grep Attached
Attached scsi disk sdb State: running

Format the disk as ext3 and mount the volume.

# mkfs.ext3 /dev/sdb
# mkdir -p /export
# mount /dev/sdb /export

Add the disk to /etc/fstab to make sure it gets mounted on boot.
```
/dev/sdb /export ext3 _netdev 0 0
```

Now you can set up /export as an NFS share.

Limiting NFS export. In order to avoid data loss, it is highly recommended that you limit the NFS export to a particular subnet by specifying a subnet mask (e.g.,”192.168.1.0/24”). By allowing access from only within the expected cluster, you avoid having non-pool member mount the storage and inadvertently delete all its data. The limit you place must include the management network(s) and the storage network(s). If the two are the same network then one CIDR is sufficient. If you have a separate storage network you must provide separate CIDRs for both or one CIDR that is broad enough to span both.
The following is an example with separate CIDRs:
```
/export 192.168.1.0/24(rw,async,no_root_squash,no_subtree_check) 10.50.1.0/24(rw,async,no_root_squash,no_subtree_check)
```
Removing the async flag. The async flag improves performance by allowing the NFS server to respond before writes are committed to the disk. Remove the async flag in your mission critical production deployment.