Bookshelf v7.5: Using a Redundant Disk Array

RAID devices—arrays of physical disks—can provide large amounts of I/O throughput and capacity while appearing to the operating system and RDBMS as a single large disk (or multiple disks, as desired, for manageability). The use of RAID arrays can greatly simplify the database layout process by providing an abstraction layer above the physical disks while promoting high performance.

NOTE: Performance of the RAID feature provided by Operating System is not satisfactory. You should use the RAID provided by you hardware vendors for better performance.

Table 24 describes a sample disk layout for a server dedicated to Microsoft SQL Server, where the database uses a single filegroup residing on a disk array. The use of a single RAID array for the database devices provides satisfactory performance in many cases without the administrative overhead of using individual filegroups.

Table 24. Microsoft SQL Server Recommended Disk Layout
Disk	Objects	Comments
Single mirrored	Windows OS	N/A
Single disk	Windows pagefile	Segregate for maximum performance.
Single mirrored	SQL Server logfile	Segregate sequential I/O for database performance.
3-5 disks (minimum) in a RAID configuration	Siebel Database data and indexes	Add as many spindles as required for performance and storage capacity.

If your Enterprise requires the highest performance standards, you should create heavily used tables and their corresponding indexes, such as those listed under Planning the Distribution of Your Database Objects on a specific SQL server filegroup within your database. By creating a filegroup on a specific disk or on multiple disks, you can control where tables and indexes in your database are physically located. For a discussion of this, see Logical Device Layout.

Use of RAID devices, and following Microsoft's recommended default disk layout, has the advantage of avoiding the need to perform the complex calculations required to size your database when separating database objects into individual filegroups.

Your choice to use RAID devices or multiple filegroups to distribute database objects, will depend solely on how great your performance needs are. It is recommended that you work with your hardware vendor to determine the optimal RAID configuration for your specific requirements.