Racks:
• 19″ standard called EIA-310-E, which is essentially equivalent to IEC-60297-3-100 or DIN 41494
• 1U = 1.75″, 42U means that any combination up to 42 (21 x2U, 7 x 6U, etc). Common sizes 42U, 45U and 48U

• Cage nuts and rails – 2-4 rails, cage nuts go into square hole on the rack to receive screws. Round holes are threaded.
• Wheels vs slides ???
• Doors vs no doors – affects ventilation, back doors are split, hot rows vs cold rows,
• Sides vs no sides – baying them together = bolting several racks together so that the hot side is kept separate from the cool side.
• Weight issues on flooring static vs dynamic rating for weight, could be the same if heavy castors
○ When rolling a rack, with or without installed equipment, you should always push it away from you—not pull it toward you. Push along its longest axis, which is almost always from front to back or back to front.
• Space issues for servicing-
○ Width: standardized 24″ wide, some 30″ wide;
○ Depth: 42″ deep but sometimes 48″ deep. Mid-depth 36″, shallow depth 32″
○ Doors split in back for clearance
• Space issues within –
○ Mount PDUs vert/horz – vertical uses no rack space and is called 0U
○ Cable management
Cooling – computer room air conditioners (CRACs). Using “close-coupled” CRACs can increase efficiency compared to traditional perimeter CRACs.