Distributed Replicated Block Device (DRBD) in Netezza
Distributed Replicated Block Device (DRBD) is a block device driver that can replicate disk, partition, blocks, etc across different Linus database hosts in a HA cluster environment. Here are some of the high-level details on how DRDB works in Netezza appliance.
- Netezza uses DRBD to replicate /nz and /export/home mount points from active (primary) host to passive (secondary) host
- Data on primary host is committed only when it is written to secondary host i.e. synchronous replication is used
- Synchronous replication helps in avoiding data loss incase of failover
- Read activity from above mount points always take place in active host
- Never stop DRBD service until or unless recommended by Netezza support. NOTE: This can result in brain split. A condition when both the nodes will have different data image
How to check DRBD service ?
DRBD service status can be checked by using one of the below two methods:
- Run “service drbd status” command in Unix host
- Run “cat /proc/drbd” command in Unix host