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Question 48/49
A MySQL server was initialized with separate UNDO tablespaces. Users complain that when they roll back large transactions, the time to process the request takes too long. The DBA would like to move the MySQL InnoDB UNDO tablespace to a solid-state drive (SSD) for better performance. Is this possible and how?
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14.6.3.4 Undo Tablespaces
Undo tablespaces contain undo logs, which are collections of undo log records that contain information about how to undo the latest change by a transaction to a clustered index record. Undo logs exist within undo log segments, which are contained within rollback segments. The innodb_rollback_segments variable defines the number of rollback segments allocated to each undo tablespace.
Undo logs can be stored in one or more undo tablespaces instead of the system tablespace. This layout differs from the default configuration in which undo logs reside in the system tablespace. The I/O patterns for undo logs make undo tablespaces good candidates for SSD storage, while keeping the system tablespace on hard disk storage.
The number of undo tablespaces used by InnoDB is controlled by the innodb_undo_tablespaces configuration option. This option can only be configured when initializing the MySQL instance. It cannot be changed afterward.