Concatenation Guidelines

• A concatenated metadevice uses less CPU time than striping.

• Concatenation works well for small random I/O.

• Avoid using physical disks with different disk geometries.

  Disk geometry refers to how sectors and tracks are organized for each cylinder in a disk drive. The UFS organizes itself to use disk geometry efficiently. If slices in a concatenated metadevice have different disk geometries, DiskSuite uses the geometry of the first slice. This fact may decrease the UFS file system efficiency.

Disk geometry differences do not matter with disks that use Zone Bit Recording (ZBR), because the amount of data on any given cylinder varies with the distance from the spindle. Most disks now use ZBR.

• When constructing a concatenation, distribute slices across different controllers and busses. Cross-controller and cross-bus slice distribution can help balance the overall I/O load.