The most data ever read and written in a second

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26,888 gibibytes a second

Held by SCNet AICS-A. Set 2026-06-12, and has stood for 109 days. Written down here 2026-09-13.

Every other number on this page is arithmetic, or a score on a test. This one is data in motion. A supercomputer keeps its storage in a separate machine from its processors, and this benchmark measures how fast the two can talk: thousands of processes write one enormous file at once, read it back, and then do both again with the scattered, awkward access pattern that real work actually has. A gibibyte is a little over a billion bytes, so twenty-six thousand of them a second is about a billion bytes every thirty-five microseconds. The record does not climb steadily, because there is no continuous race here - there are individual buildings, each arriving all at once. The oldest submissions this list still carries are from November 2019, where the best figure was 209. It reached 11,362 with Argonne's Aurora in November 2023, then did not move for five lists and two and a half years, until June 2026, when it more than doubled.

That description was written when this frontier was opened, on 2026-09-13, and is never rewritten. Where it and the number above it disagree, the number is the reading and the description is history.

What counts

The largest bandwidth figure in the Full List of the current IO500 edition - the benchmark's own BW column, which is the geometric mean of its four large-file phases, the easy and hard writes and the easy and hard reads. The Full List carries every valid submission ever made rather than one list's worth, so its largest figure is an all-time record. It is not rank one: the lists are ranked on a composite score of bandwidth and metadata rate together, and the bandwidth maximum sits some rows below the top. The current edition is reached from the list index, and that list's own Download link serves the whole thing as a CSV file.

What moves it

A new IO500 list is published, twice a year at the ISC and SC conferences, carrying a submission with a larger bandwidth figure than any before it.

Where to check it: https://io500.org/list/

Last checked: 2026-09-28

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