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We Include Free of charge CDP for MYSQL with all Shared hosting accounts.
What does MySQL Agent add-on actually do? Do I really need it? Won't CDP get a good backup of my MySQL databases without it?
R1Soft CDP for Linux does perform point-in-time snapshot (A.K.A. open file backups) for Linux. The snapshot means we take a flush all uncommitted changes to the file system still in memory to disk and snapshot the state of the file system. It is not possible for us to know what Linux or Windows applications have open in memory that has never been written to disk or may be partially written. Its all application specific.
The MySQL MyISAM database makes changes to the MyISAM files and it does NOT use an on-disk rollback journal file. This means MyISAM files will be corrupted if they are copied while they are being written to and a special query "FLUSH TABLES WITH READ LOCK" is not precisely coordinated with the file system snapshot performed by CDP.
The MySQL add-on requires you to specify a MySQL account with administrative privileges that is used by the Linux Agent to FLUSH TABLES WITH READ LOCK before the file system snapshot is taken. And the lock must be held until the snapshot completes. If we do not do this your MyISAM tables will be corrupted.
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