(mysql.info.gz) InnoDB Disk I/O

Info Catalog

(mysql.info.gz) File space management

(mysql.info.gz) File space management

(mysql.info.gz) InnoDB Raw Devices

 
 15.15.1 Disk I/O
 ----------------
 
 `InnoDB' uses simulated asynchronous disk I/O: `InnoDB' creates a
 number of threads to take care of I/O operations, such as read-ahead.
 
 There are two read-ahead heuristics in `InnoDB':
 
    * In sequential read-ahead, if `InnoDB' notices that the access
      pattern to a segment in the tablespace is sequential, it posts in
      advance a batch of reads of database pages to the I/O system.
 
    * In random read-ahead, if `InnoDB' notices that some area in a
      tablespace seems to be in the process of being fully read into the
      buffer pool, it posts the remaining reads to the I/O system.
 
 Starting from MySQL 3.23.40b, `InnoDB' uses a novel file flush technique
 called doublewrite.  It adds safety to crash recovery after an
 operating system crash or a power outage, and improves performance on
 most Unix flavors by reducing the need for `fsync()' operations.
 
 Doublewrite means that before writing pages to a data file, `InnoDB'
 first writes them to a contiguous tablespace area called the
 doublewrite buffer. Only after the write and the flush to the
 doublewrite buffer has completed does `InnoDB' write the pages to their
 proper positions in the data file. If the operating system crashes in
 the middle of a page write, `InnoDB' later will find a good copy of the
 page from the doublewrite buffer during recovery.
 

Info Catalog

(mysql.info.gz) File space management

(mysql.info.gz) File space management

(mysql.info.gz) InnoDB Raw Devices