The PDU tripped at 11:47 AM on a Tuesday.<\/p>\n\n\n\n
Not during burn-in. Not during failover testing. During a routine firmware update on a switch rack that had been running fine for six months.<\/p>\n\n\n\n
The data center team in Hong Kong had sized the rack perfectly. Or so they thought.<\/p>\n\n\n\n
Each switch base load was around 450W. The rack PDU was rated for 6kW. Plenty of headroom, right?<\/p>\n\n\n\n
They had forgotten to account for 512 QSFP28 LR4 modules drawing roughly 4.5W each. That was 2,304W of optics power alone. Add the base load from eight fully populated QSFP28 switches, and the rack was pulling close to 5,900W before transient load, fan ramp-up, or future expansion.<\/p>\n\n\n\n
No 80% planning margin. No room for power spikes. The breaker did not hesitate.<\/p>\n\n\n\n
Four days of production delay. All because the power budget math skipped a line.<\/p>\n\n\n\n
QSFP28 power consumption is not a spec-sheet curiosity. It is a rack design constraint that determines PDU sizing, cooling capacity, and whether your deployment stays stable in summer heat. This guide gives you the per-module wattage data, the switch-level math, and the thermal framework to plan it right the first time.<\/p>\n\n\n\n
New to QSFP28? Our <\/em>complete QSFP28 guide<\/em><\/u><\/em><\/a> covers form factor basics, module types, and compatibility.<\/em><\/p>\n\n\n\n