Improved InnoDB I/O scalability¶
Because InnoDB is a complex storage engine it must be configured properly in order to perform at its best. Some points are not configurable in standard InnoDB. The goal of this feature is to provide a more exhaustive set of options for XtraDB.
System variables¶
innodb_flush_method¶
| Option | Description |
|---|---|
| Command-line | Yes |
| Config file | Yes |
| Scope | Global |
| Dynamic | No |
| Data type | Enumeration |
| Default | NULL |
| Allowed values | fsync, O_DSYNC, O_DIRECT, O_DIRECT_NO_FSYNC, littlesync, nosync |
The following values are allowed:
-
fdatasync: usefsync()to flush data, log, and parallel doublewrite files. -
O_SYNC: useO_SYNCto open and flush the log and parallel doublewrite files; usefsync()to flush the data files. Do not usefsync()to flush the parallel doublewrite file. -
O_DIRECT: use O_DIRECT to open the data files andfsync()system call to flush data, log, and parallel doublewrite files. -
O_DIRECT_NO_FSYNC: use O_DIRECT to open the data files and parallel doublewrite files, but does not use thefsync()system call to flush the data files, log files, and parallel doublewrite files. Do not use this option for the XFS file system.
Note
On an ext4 filesystem, set innodb_log_write_ahead_size to match the filesystem’s write-ahead block size. This variable avoids unaligned AIO/DIO warnings.
Status variables¶
The following information has been added to SHOW ENGINE INNODB STATUS to confirm the checkpointing activity:
The current checkpoint age target
The current age of the oldest page modification which has not been flushed to disk yet.
The current age of the last checkpoint
...
---
LOG
---
Log sequence number 0 1059494372
Log flushed up to 0 1059494372
Last checkpoint at 0 1055251010
Max checkpoint age 162361775
Checkpoint age target 104630090
Modified age 4092465
Checkpoint age 4243362
0 pending log writes, 0 pending chkp writes
...
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