Reviewing enclosure location guidelines

The control enclosure requires two standard rack units of space in a rack. If you plan to add expansion enclosures in the future, follow the guidelines for a control enclosure plus one or more expansion enclosures.

• Each control enclosure requires two standard rack units of space in a rack.
  Important: The control enclosure must have a 12 Gb SAS adapter installed (feature code AHBA) to use expansion enclosures, as the SAS enclosures are connected to port 1 and port 3 of the adapter.
• Position the control enclosure in the center of the rack to make cabling easier. Balance the number of expansion enclosures above and below the control enclosure
• Position the enclosures together. Avoid adding other equipment between enclosures.
• Position the enclosures in the rack so that you can easily view them and access them for servicing. This action also allows the rack to remain stable and allows two or more people to install and remove the enclosures.
• A maximal configuration spans multiple racks. If multiple racks are required, locate the racks next to one another.
• Attach no more than 10 2U or 4 5U expansion enclosures to port 1 and port 3 of the control enclosure.

  Your system supports specific combinations of SAS expansion enclosures, based on the capacity of each of the enclosures.

  To limit contention for bandwidth on a chain of SAS enclosures, a maximum of four high-density expansion enclosures ( 2076-92G ) can be installed in the chain. High-density enclosures and standard-density enclosures ( 2076-12G and 2076-24G ) can be mixed within a chain, based on the following rules:

  • A chain is allowed to have expansions with a total “weight” of 10.
  • Standard-density enclosures are assigned a weight of 1.
  • A high-density expansion enclosure is assigned a weight of 2.5.
  The following table shows examples of expansion enclosure configurations based on these guidelines:

  Table 1. Sample configurations of expansion enclosures per control enclosure

  Expansion enclosures per node	Allowable configurations per control enclosure
  10	10 standard-density expansion enclosures
  8	One high-density expansion enclosure, seven standard-density expansion enclosures or Eight standard-density expansion enclosures
  7	Two high-density expansion enclosures, five standard-density expansion enclosures or Seven standard-density expansion enclosures
  5	Three high-density expansion enclosures, two standard-density expansion enclosures or Five standard-density expansion enclosures
  4	Four high-density expansion enclosures

Each 2U enclosure requires two standard rack units of space in a rack. Identify the appropriate location for each enclosure by using the numbers on the front of the rack. When you add a single expansion enclosure to an existing network, it is preferable to add the enclosure directly below the control enclosure. When you add a second expansion enclosure, it is preferable to add the enclosure directly above the control enclosure. As more expansion enclosures are added, alternate adding them above and below the control enclosure.

The 5U (5U-92) expansion enclosures are larger and heavier than 2U enclosures. As such, you should avoid installing the 5U expansion enclosure above position 22U in the rack.

Put the second set of enclosures above or below the first set of enclosures. You can also add the second set of enclosures in a different rack.