This section describes the LifeKeeper for Linux DRBD Recovery Kit configuration details. It also contains information you should consider before you start to configure and administer the DRBD Recovery Kit. Please refer to LifeKeeper for Linux Technical Documentation for instructions on configuring LifeKeeper Core resource hierarchies.
Network Bandwidth Requirements
Prior to installing DRBD, you should determine the network bandwidth requirements for replicating your current configuration whether you are employing virtual machines or using physical Linux servers. Use the method Measuring Rate of Change on a Linux System to measure the rate of change for the system that you plan to replicate. This value indicates the amount of network bandwidth that will be required to replicate the systems.
After determining the network bandwidth requirements, ensure that your network is configured to perform optimally. If your network bandwidth requirements are above your current available network capacity, you may need to consider one or more of the following options:
- Increase your network capacity
- Reduce the amount of data being replicated
- Create a local, non-replicated storage repository for temporary data and swap files
Optimizing DRBD Performance
The DRBD User’s Guide in the section “Optimizing DRBD performance” provides steps to follow to measure throughput using the DRBD block device and configuration options to improve performance.
I/O Fencing with DRBD
I/O fencing is necessary in DRBD configurations to avoid a split brain where data is modified on multiple systems at the same time due to communication failure. This can result in the loss of committed data. Therefore, you need to take steps to prevent a split brain from occurring via the following controls.
Exclusive Control using IP Resources
IP resources have an exclusive control functionality using duplication checking to ensure the same IP resource is not activated on multiple servers. This can be used to avoid a split brain.
Adding an IP resource as a child resource to all DRBD resources in the hierarchy can prevent the DRBD resource from starting on multiple servers at the same time.
This method can only be used in environments where all the servers in the cluster reside in the same subnet. This is required to perform the duplicate IP address checking.
Exclusive Control with Quorum/Witness Functionality
You can use the quorum/witness functionality in LifeKeeper to prevent multiple nodes from becoming active at the same time.
For details, please refer to the Quorum/Witness topic in the Technical Documentation.
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