Disk considerations

Because database operations are often I/O-intensive, a faster, dedicated disk can improve how the database performs. Use high-performance disks whenever possible to ensure optimum database operation.

SQL Server performs better when there is minimal disk contention. For best performance, place tempdb files, reporting database files, and log files on separate physical drives with dedicated controllers. Follow SQL Server recommendations for installing and configuring SQL Server.

RAID controllers provide disk redundancy and can increase disk throughput by spreading I/O activity across multiple physical disks. If you have a high-demand system, for peak performance, use a RAID 10 configuration managed by a hardware- based RAID controller. (For systems with a lower I/O profile, RAID 5 may provide sufficient performance at a lower cost.)

For best performance:

  • Use a hardware RAID controller, not software.
  • Max out the RAID controller RAM cache.
  • Use multi-channel links between the RAID controller and disk shelf or SAN.
  • Separate the transaction logs and database files onto separate disks, arrays, or LUNs.

    This means separate spindles or RAID arrays, not just separate logical drives.

    If you are using a SAN, map the physical and logical LUNs to ensure you are reading and writing key components to separate physical drives. (This is to enable multiple parallel I/O operations.)

  • Make sure that different database files are spread across different disks wherever possible. For very large deployments, for example, plan to map wslogdb70_1 to spindle 1, wslogdb70_2 to spindle 2, and so on.
  • The disk stripe size (how files are stored across striped arrays) is also critical and is a function of both the typical read/write size and the total database size. Contact Microsoft or a sizing specialist for guidance.
  • In large deployments, map different disks, arrays, or LUNs across different hardware controllers to maximize parallel operations and controller cache usage.
  • If you are using spinning disks, lower seek times are better.