6.4.3 Oracle Databases

Specify the noatime option when mounting volumes that host Oracle datafiles, control files, redo logs, voting disk, and OCR. The noatime option disables unnecessary updates to the access time on the inodes.

Specify the nointr mount option to prevent signals interrupting I/O transactions that are in progress.

By default, the init.ora parameter filesystemio_options directs the database to perform direct I/O to the Oracle datafiles, control files, and redo logs. You should also specify the datavolume mount option for the volumes that contain the voting disk and OCR. Do not specify this option for volumes that host the Oracle user's home directory or Oracle E-Business Suite.

To avoid database blocks becoming fragmented across a disk, ensure that the file system cluster size is at least as big as the database block size, which is typically 8KB. If you specify the file system usage type as datafiles to the mkfs.ocfs2 command, the file system cluster size is set to 128KB.

To allow multiple nodes to maximize throughput by concurrently streaming data to an Oracle datafile, OCFS2 deviates from the POSIX standard by not updating the modification time (mtime) on the disk when performing non-extending direct I/O writes. The value of mtime is updated in memory, but OCFS2 does not write the value to disk unless an application extends or truncates the file, or performs a operation to change the file metadata, such as using the touch command. This behavior leads to results in different nodes reporting different time stamps for the same file. You can use the following command to view the on-disk timestamp of a file:

# debugfs.ocfs2 -R "stat /file_path" device | grep "mtime:"