AWS Designs In-Rack Micro UPS Units for a More Efficient Cloud (Rich Miller)

Overview

The article was published by Rich Miller on Data Center Frontier in 2020. It reports AWS's move from centralized third-party UPS systems to custom rack-level battery packs and power supplies, and places it in the history of distributed UPS at Google, Facebook/OCP and Microsoft. Distributing energy storage shrinks the failure blast radius to one rack, removes conversion stages and allows battery swaps without shutdown. According to AWS, the distributed rack UPS reduces energy conversion loss in its power chain by 35%.

Batteries can be removed and replaced in seconds without powering down, and availability better than seven nines is claimed. A single UPS failure affects only one rack instead of a hall or building, eliminating a single point of failure. These are AWS's own statements, and the article offers no independent verification. The article recounts the history of the distributed approach. Google began integrating batteries into server power supplies in 2009 and later moved to 48 V to the motherboard.

Facebook's 2011 Open Compute design used in-row UPS units serving three racks and 277 V AC to servers instead of 208 V. Microsoft's 2015 Local Energy Storage put a mini-UPS in each server chassis and was contributed to OCP. Readers should bear in mind that the article is a news report and offers no technical design standard. The figures are operators' own claims and may be specific to their scale. OCP Open Rack is named as a related reference.

Key points

1. AWS said the distributed rack UPS reduces energy conversion loss in its power chain by 35%.
2. Batteries can be replaced in seconds without powering down; availability better than seven nines is claimed.
3. A single UPS failure affects only one rack instead of a hall or building, eliminating a single point of failure.
4. Google began integrating batteries into server power supplies in 2009 and later moved to 48 V to the motherboard.
5. Facebook's 2011 Open Compute design used in-row UPS units serving three racks and 277 V AC instead of 208 V.
6. Microsoft's 2015 Local Energy Storage put a mini-UPS in each server chassis and was contributed to OCP.
7. Figures are operators' own claims; there is no independent verification.

Using it in design

• Offer distributed UPS topologies (in-server, in-rack battery shelf, in-row) alongside centralized UPS, with an efficiency and blast-radius comparison.
• Model failure domains per topology in the reliability view.
• Add the number of conversion stages as an explicit input to the power chain efficiency calculation.
• Treat battery replacement without shutdown as a maintenance procedure and commissioning criterion.
• Mark OCP Open Rack compatible solutions with a separate catalog tag.

Who should read it

Electrical designers and hyperscale operations engineers comparing distributed UPS and rack-level power architectures with centralized UPS.

Related standards

• OCP Open Rack

Publication details

Authors

Rich Miller

Publisher

Data Center Frontier

Year

2020

Document language

English

Source type

Expert / community

Access

Free to read

Licence

Copyright retained; citation only — the publisher’s terms apply to the original document

Citation