Choosing dedicated or switchable IOP and devices for logical partitions

 

Although the recommended approach is to confine all hardware within a partition, this is not always a cost-effective solution. With some devices it might be preferable to share them among partitions.

IOPs that are candidates for switching include:

• IOPs that control high cost devices.

• IOPs that control low utilization devices and low demand devices.

• IOPs that solely control the target device or devices.

Although partitions do not support concurrent device sharing, IOP-level switching might be an effective solution.

• Advantages of switching IOPs and devices

  • Reduced cost.

  • Fewer card positions needed. In some cases, this could mean that you need fewer expansion units.

• Disadvantages of switching IOPs and devices

  • Inconvenience of having to schedule use of switchable IOPs and devices.

For external tape (for instance, 3590), it is possible to have one tape device, but separate IOPs for each partition that will use it. A partition requesting use of the device receives a "busy" indication if it is in use by another partition.

Before implementing a switchable IOP and other devices, you should also consider other possible alternatives. To share devices among partitions, you can apply the same techniques that are used to share devices among separate physical servers:

• Use multiple IOPs, one in each partition, for devices that support multiple connections (some high end tape drives).

• Use multiple IOPs, one in each partition and use a switch box for devices that only support single connections (printers, or some high end tape drives).

• Use multiple IOPs and multiple devices in each partition for a self-contained solution (internal removable media devices).

 

Parent topic:

Hardware requirements for logical partitions

Related concepts
Selecting bus-level or IOP-level partitioning