MySQL

This Protected Item type backs up a MySQL database. It is also compatible with MySQL-compatible servers such as MariaDB, Percona Server for MySQL, and TiDB. It works at the logical (SQL) level.

No data is spooled to the local disk. As per the "Program Output" type, no progress bar or ETA appears during a MySQL backup. The data is fed directly into the Comet compression and encryption 'chunking' engine. There is a quick cryptographic hash-check to determine whether these chunks are duplicated in the storage location, and then any new chunks are sent directly to the Storage Vault.

Databases are backed up one-at-a-time. Point-in-time consistency is only preserved on a per-database basis.

Connection details

Connection details should be supplied before selecting databases. Fill in the fields on the Authentication tab to connect to your MySQL server.

Comet always connects to the MySQL server over TCP, using an IP address and port. Using a Unix socket file is not currently supported.

As of Comet 21.9.7, Comet supports configuring SSL / TLS parameters to secure the MySQL TCP connection.

• You can configure whether to allow self-signed server SSL certificates, or supply a path to a server CA file or directory.
• You can configure paths to a client SSL certificate. The client certificate should be in PEM (x.509) file format, usually with the .crt and .key file extensions.

Selecting databases

Use the plus button on the right to open a database browser, allowing you to select individual databases for backup. Use the dropdown-plus button to add a custom property.

Custom mysqldump

Comet Backup's MySQL support works at the logical (SQL) level using mysqldump. A copy of this program must be found on the device in order for the backup job to run.

The mysqldump binary is selected as follows:

• If a custom path to mysqldump has been set, this binary is used.
• Otherwise, if there is a version of mysqldump installed (e.g. you are backing up a MySQL server from the server itself), the local version of mysqldump will be used to ensure maximum compatibility.
• Otherwise, if no copy of mysqldump can be found, the Windows version of Comet Backup bundles a recent mysqldump binary in compliance with its license.
• If no suitable mysqldump binary is found, the MySQL backup job will fail with an error message Couldn't find 'mysqldump' anywhere. This failure can be detected via the backup job's status or its log entries.

On Linux, you can install a copy of mysqldump as follows:

Distribution	Command
Debian, Ubuntu	apt-get install mysql-client
CentOS, RHEL	yum install mysql

System databases

Comet supports backing up the built-in system databases if desired.

• The mysql database contains server configuration, including user accounts and grants. It should only be restored to the same major release of MySQL.
• The information_schema database is a set of read-only views and does not need to be restored.
• The performance_schema database is a set of aggregated statistics and does not need to be restored.
• The sys database (in MySQL 5.7.7 and higher) is a set of performance statistics and does not need to be restored. If your version of MySQL does not successfully back up this table, it is safe to exclude it from the Comet Backup settings.

Stored Procedures

Tables which contain stored procedures can be restored, but be aware that the login user must have SYSTEM_USER and SET_USER_ID privileges.

Isolation modes

Comet allows you to select the isolation mode used when reading data from MySQL. You should select the most appropriate isolation mode for your MySQL engine type.

The following options are available:

Isolation Mode	InnoDB	MyISAM	Detail
Transaction	Consistent	Inconsistent	Wrap all read access in a single transaction, so that the read data is consistent
Lock tables (default)	Consistent, but slow	Consistent, but slow	Lock access to database before reading it, so that the read data is consistent. This requires that the MySQL user account has been granted the LOCK TABLES permission
None	Inconsistent	Inconsistent	Do not take a transaction and do not lock tables.