The speed with which the database system can read data from the volumes and write data to the volumes has a significant influence over the performance of the database instance. To achieve good I/O performance when you later operate the database instance, use the following tips when you create and configure a new database instance.
· If you are operating several database instances, then create each database instance on a separate computer.
· Use different disks for data volumes and for log volumes. As the database system logs all data changes in the log volumes, the log volumes are the areas of the database instance with the highest write activity.
· For swap and paging areas, use different disks than for the log volumes.
· Mirror the log area and the data area using hardware-based means, for example by using RAID-5 or RAID-1 systems. When you select the RAID system, note that the RAID Controller has a good write performance and that caches can still be saved to disk even when there is a power outage.
· Even if you are using RAID-5 systems, create several data volumes for the database instance. Because some of the database system’s parallelization techniques depend on the number of data volumes, you can improve performance if you use several data volumes instead of one data volume.
· If you are using several disks for the volumes, use disks with standardized performance data, in particular standardized access speeds. This is the only way to ensure that the disks are filled evenly.
· If you are using fault-tolerant hardware, then expand the capacity only using the same type of hardware. For example, expand RAID-5 systems with RAID-5 systems only.
· Do not create log volumes on RAID-5 systems, but only on dedicated disks or on RAID-1 systems.
· On UNIX systems, use raw devices for data and log volumes. Accessing data in raw devices is usually faster than accessing data in files.
· Choose suitable log settings for your database system:
¡ If hardware-based mirroring of the log area is not possible, then configure the log mode so that the database system mirrors the log area.
¡ Switch off the overwrite mode for the log area.
¡ Always leave the redo log management switched on.
See also:
Creating and Configuring a Database Instance