MariaDB Galera Multi-Master Performance

Question

I am playing around with a MariaDB Galera Multi Master Cluster and I have some performance issues which I do not understand.

I have 2 virtual test machines with Ubuntu 16.04 and MariaDB 10.1 installed. I wrote a simple "benchmark" tool which simulates the creation of a contact in an example application. If I run this benchmark on a single machine, I get around 1050 transactions per seconds on each machine. I did not change anything on the default configuration of mariadb.

If I now cluster those two machines together via galera to a multi-master cluster, I get a significant performance drop to around 99 transactions per second.

The two machines are connected via a Gigabit network. I measured the throughput with iperf and its 950Mbits. The ping times are around 0.35ms. The galera configuration is:

[galera]
# Mandatory settings
wsrep_on=ON
wsrep_provider=/usr/lib/galera/libgalera_smm.so
wsrep_cluster_address="gcomm://192.168.193.220,192.168.193.221"
binlog_format=row
default_storage_engine=InnoDB
innodb_autoinc_lock_mode=2
wsrep_sst_method=rsync
wsrep_node_address=192.168.193.220
wsrep_cluster_name="DB Cluster"

I do not wonder about the absolute transactions per second, but about the relative drop from a standalone instance to the cluster. What am I missing?

Answer 1

I don't know about your application/workload but generally, you should try with:

• wsrep_slave_threads=N (Do not use a value for wsrep_slave_threads that is higher than the average given by the wsrep_cert_deps_distance status variable)
• innodb_flush_log_at_trx_commit=0 (default is 1)
• Have you tried redirect all writes to one node and leave the other as a hot-backup? Some workloads get a huge improvement by doing this.