In the following section, we provide answers to questions that are most frequently asked about DRBD Architecture.

Questions

Questions and Answers

B.14.3.1: Is an Active/Active option available for MySQL with DRBD?

Currently, MySQL does not support Active/Active configurations using DRBD “out of the box”.

B.14.3.2: What MySQL storage engines are supported with DRBD?

All of the MySQL transactional storage engines are supported by DRBD, including InnoDB and Falcon. For archived or read-only data, MyISAM or Archive can also be used.

B.14.3.3: How long does a failover take?

Failover time is dependent on many things, some of which are configurable. After activating the passive host, MySQL will have to start and run a normal recovery process. If the InnoDB log files have been configured to a large size and there was heavy write traffic, this may take a reasonably long period of time. However, under normal circumstances, failover tends to take less than a minute.

B.14.3.4: How long does it take to resynchronize data after a failure?

Resynchronization time depends on how long the two machines are out of communication and how much data was written during that period of time. Resynchronization time is a function of data to be synced, network speed and disk speed. DRBD maintains a bitmap of changed blocks on the primary machine, so only those blocks that have changed will need to be transferred.

B.14.3.5: Are there any situations where you shouldn't use DRBD?

See When Not To Use DRBD.

B.14.3.6: Are there any limitations to DRBD?

See DRBD limitations (or are they?).

B.14.3.7: Where can I find more information on sample architectures?

For an example of a Heartbeat R1-compatible resource configuration involving a MySQL database backed by DRBD, see DRBD User's Guide.

For an example of the same DRBD-backed configuration for a MySQL database in a Heartbeat CRM cluster, see DRBD User's Guide.