Adaptive Server allows you to control the placement of databases, tables, and indexes across physical storage devices, which can improve performance by equalizing the reads and writes to disk across many devices and controllers. For example, you can:
Place database data segments on a specific device or devices, storing the database log on a separate physical device so that reads and writes to the log do not interfere with data access.
Spread large, heavily used tables across several devices.
Place specific tables or nonclustered indexes on specific devices. For example, you might place a table on a segment that spans several devices and its nonclustered indexes on a separate segment.
Place the text and image page chain for a table on a separate device from the table. The table stores a pointer to the actual data value in the separate database structure, so each access to a text or image column requires at least two I/Os.
Distribute tables evenly across partitions on separate physical disks to provide optimum parallel query performance and improve insert and update performance.
For multiuser and multi-CPU systems that perform a lot of disk I/O, be especially aware of physical and logical device issues and the distribution of I/O across devices:
Plan a balanced separation of objects across logical and physical devices.
Use enough physical devices, including disk controllers, to ensure physical bandwidth.
Use an increased number of logical devices to ensure minimal contention for internal I/O queues.
Determine and use a number of partitions that allows parallel scans and meets query performance goals.
