This AppNote describes how to configure NFSv4 on iSCSI-based Linux High Availability (HA) clusters.
Table of Contents
- Cluster Terminology
- Minimum System Requirements
- iSCSI Target Configuration on Linux
- iSCSI Initiator Configuration on Linux
- Configuring Heartbeat on Nodes
- Configuring Resources for NFSv4
1. Cluster Terminology:
Following are the few terms used in clustering.
Clustering is a technique in which two or more servers are interconnected and can access a common storage pool. Cluster Services enables you to combine a number of servers together into a single group, known as a cluster. One of the primary benefits of Cluster Services is that it provides failover capabilities to your server clusters. If one server in the cluster should happen to fail, another server automatically recovers the downed-server’s resources and runs in its place.
The iSCSI protocol combines the use of block-level data movement with TCP/IP networks. By allowing SCSI commands to travel through IP networks, high-speed IP networking technology can carry data from storage units to servers anywhere throughout a corporate network. Also referred to as IP storage
iSCSI Target and Initiators:
Target is the device which is mostly configured as the common storage for all the hosts in a network. Any server can be configured as iSCSI target. It is a virtual disk which is created on the Linux server and allows the remote access over an Ethernet connection by iSCSI initiators.
Initiator is any node in the network which is configured to contact the target for services. In general your target should be always up and running so that any host acting as initiator will be able to contact the target.
In Active passive clusters, only one node is active at a time. Other nodes get the resource only in case of failover. When failover takes place, the resource migrates from the node where there is failure to the other node. After migration, it restarts all the services on the current node. And now this node becomes active. When the failed node resumes, the resource migrates back to its original node and this is called failback.
High Availability (HA):
This is done in order to improve the availability of the resource to the node at all times. When one node in a cluster goes down, the resource migrates to another node in the cluster and this node takes the responsibility of servicing so the resource is available at all times. HA clusters are designed for fault tolerance.
2. Minimum System Requirements:
Three server class machines:
- Two machines for Linux iSCSI initiator.
- One Linux machine for iSCSI target
- SUSE Linux Enterprise Server 10
Before installation of target and initiators on the machine, make sure that you have enough space to configure a common storage device. This machine will act as a target. When the hardware is selected, install iSCSI target packages from YaST2.
On the other two nodes, install the iSCSI initiator packages. This can be done after installing SLES 10.
Make sure that you have installed the heartbeat packages on all of the nodes. This can be done later.
4. iSCSI Target Configuration on Linux
Follow the steps below to configure the iSCSI target server:
- Create a block device on the target machine.
- Type yast2 disk in the terminal.
- Create a new Linux partition and select Do not format.
- Do not mount the partition.
- Select partition size depending upon the usage.
- In the terminal type:
If the iSCSI target is not installed on the server, click Continue on the popup window to install the iSCSI target software. (This popup window will show only if the iSCSI target server packages are not installed on the system).
- Click on the Service tab and select When Booting in Service Start.
- Go to Global and click Next to continue. In the next screen go to Targets and click on the Add option and enter the path as /dev/hdax as created in step 1. If there is already a target, then delete the target and add a new one.
This partition will be used as common storage for all the nodes on the HA clusters.