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Getting your data centre ready for Open Compute and Open19 rack layouts

“The Open Compute Project (OCP) is a community and movement founded by Facebook that, through open source sharing and collaboration on data center designs, strive to deliver ever more innovative, scalable, efficient infrastructure solutions to meet growing industry needs, which are rapidly outgrowing conventional datacenter hardware.” Open Compute

“The Open19 platform is an open standard to define a new server form factor. It is a standard that also defines data and power distribution but not the internal design of the servers to enables server design partners to innovate and build their own servers to create a competitive landscape.” OPEN19

So what does the future layout of the data centre look like: OCP, Open19 or standard 19 inch layout in 600/800 mm racks, or a mixture of all three?

Let’s start by summarising what these terms mean.

Traditional 19 inch

What we think of as ‘standard’ 19 inch racks was formalised in EIA-310-D, Cabinets, Racks, Panels, and Associated Equipment, originally published in 1992. Although there is an IEC standard from 1986 on the same topic, IEC 60297-1:1986 Dimensions of mechanical structures of the 482.6 mm (19 in) series. Part 1: Panels and racks.

19 inch refers to the maximum width of the equipment and the two supporting rails on either side. In metric it is 483 mm.

The vertical height of equipment is measured in U or sometimes ‘RU’ (Rack Units). One U is 44.5 mm and equipment normally comes in whole units of ‘U’ e.g. 2U, 4U etc. The actual size of the equipment is slightly less than 44.5 mm to make sure they can all actually fit on top of each other in the rack.

The vertical height of the rack is also measured in U and the most common is 42U. A 42U rack is about 2m high when the top and bottom parts of the frame are taken into account.

Although the equipment width is 19 inches or 483 mm, to accommodate power and data cabling the actual cabinet width is at least 600 mm, with 750 and 800 mm also common. Note that some American racks are actually 24 inches which is of course 610 mm.

Rack depths can be 800, 1000, 1100 or 1200 mm.

The average data centre today tends to standardise on 800 x 1200 mm x 42U racks.

The vast majority of IT equipment comes in a 19 inch format. The only exception is some telecommunications equipment which tends to follow the ETSI ETS 300 119 standard which is 21.1 inches/535 mm.

Traditional 19in. Rack

Open Compute Project, OCP

The Open Compute Project’s mission is to design and enable the delivery of the most efficient server, storage and data center hardware designs for scalable computing. The initiative was announced in April 2011 by Facebook to openly share designs of data center products. The effort came out of a redesign of Facebook’s data center in Prineville, Oregon.

The principal member of OCP today are Facebook, IBM, Intel, Nokia, Google, Microsoft, Seagate Technology, Dell, Rackspace, Cisco, Goldman Sachs, Fidelity, Lenovo and Alibaba Group.

The aim is to get faster rollout of more efficient and dense data centres by the standardisation of server and storage equipment sizes. The main element of improved efficiency is the Direct Current, DC, power distribution which takes away one layer of the existing AC-DC conversion seen in standard IT equipment.

Sales of servers, networking switches, storage, peripherals, racks, power infrastructure, and other data center gear based on OCP designs generated $1.2 billion in revenue in 2017, or less than 1 percent of the $137 billion data center hardware market, according to marketing research company IHS. That’s not counting OCP hardware bought by Facebook, Microsoft, Rackspace, and Goldman Sachs, the four end-user companies with OCP board seats.

Some of the principal OCP elements are;

  • 600 mm wide rack but equipment is 21 inches (538 mm) instead of conventional 19 inch
  • Rack height 2210 mm and 1067 mm depth
  • Instead of Rack Units (44 mm) OpenU of 48 mm is used
  • Servers slide directly into 12 V dc busbars at the back
  • Two powerzones with integral UPS per rack
  • 13.2 kW per rack
  • Up to 1400 kg per rack

OCP rack are designed for hot aisle/cold aisle operation and all equipment is accessible from the front (cold aisle) side.

There is an OCP audit standard that allows users to judge if their data centre will be suitable for OCP layouts. It covers;

  • Building access including door widths and ramp slopes
  • Floor loading and room heights
  • Electrical distribution methods (essentially a 2N distribution model is required)
  • Cooling method based on 13.2 kW rack density
  • Air temperatures, quality and filtration standards
  • 3 Level cabling scheme (Intra-Pod cabling; Inter-Pod cabling; OOB cabling (Out-of-Band))
  • Local and remote monitoring capability
  • PUE, CUE and WUE metric monitored



Open19 was started in 2017 by LinkedIn and supported by companies such as HP Enterprise and GE Digital and now supported generally by people that make racks and servers.

“The Open19 platform is an open standard to define a new server form factor. It is a standard that also defines data and power distribution but not the internal design of the servers to enables server design partners to innovate and build their own servers to create a competitive landscape.” OPEN19

The Open19 platform has the following ambitions;

  • Create an open standard for 19-inch rack environment for server, storage, and networking.
  • Optimize rack deployment cost.
    • Reduce common infrastructure cost by 30% to 40%
    • Reduce server cost by 15% to 20%
  • Enable faster rack integration, 7 to 10 times faster
  • Build an ecosystem that can consolidate requirements and volumes with a high adoption level
  • Accommodate with different sizes of data centers and edge solutions.

The Open19 project offers operators of data centers and edge solutions an optimized open platform. This platform is meant to be installed to any existing or new 19-inch rack and targeted to operate as a standalone disaggregated platform that only requires a 19- inch rack and 10°C to 40°C operating environment.

The Open19 platform has four main building blocks and two optional ones:

  • Any 19-inch 4-post rack – The Open19 standard does not specify the rack. Any rack that is EIA compatible and at least 1000mm deep can be used.
  • Brick cage – A structure that creates the common, cross supplier, and form factor.
  • Data cable and power cable for the servers creating blind mate connectivity with predefined pinouts.
  • Bricks – The Open19 platform defines four form factors:
    • Brick- 1RU half width
    • Double Wide Brick (DW) – 1RU full width
    • Double High Brick (DH) – 2RU full width
    • Double High Half Width Brick (DHHW) – 2RU half width
  • Power shelf – There are two types. One is up to 19.2KW in 1RU, the other is up to 38.4KW in a 2RU.
  • Network switch – Eliminate the need for server DAC (Direct Attach Cable). The switch is optional but highly recommended. Standard switch can be used with the appropriate data cable.
  • Optional Battery backup unit (BBU)

With the standardised server ‘bricks’ the idea is to achieve rapid installation with minimal skilled labour and probably sees edge data centres and 5G base stations as a principal target. The amount of cooling to achieve 19.2 kW cooling per rack is extremely ambitious and equates to about one and a half cubic metres of air per second per rack!

“Open19 moves all cabling to the back of the rack, and the connectors are designed so that a new server slides into place and connects. That means a delivery driver could theoretically replace a server without accidentally disconnecting something, damaging a connection, or compromising airflow by leaving cables in the wrong place.” 

Picture credit OPEN19 TM


Although most data centres will still have conventional equipment racks they still require security of power and cooling. OCP and OPEN19 are movements towards greater standardisation of data centre IT products to speed up deployment with lower-skilled personnel. They add additional demands on the data centre infrastructure due to higher weights and higher power and cooling densities.

Capitoline Ltd has unrivalled experience in auditing data centres to existing standards such as TIA942 and EN50600 and can also provide OCP audit and gap analysis services.

Contact Capitoline today for advice.

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