# Straggler

A single task that runs far longer than its peers and holds up completion of the whole run.

Source: https://university.eugo.io/glossary/straggler

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A run finishes when its slowest partition finishes, so one oversized piece of work erases the benefit of splitting the rest evenly. Uneven partitions are the usual cause, not slow hardware.

## Related terms

- [Long tail](https://university.eugo.io/glossary/long-tail) — The situation where most tasks finish quickly but one or two run much longer, so the whole run waits on them while workers sit idle.
- [Partition](https://university.eugo.io/glossary/partition) — One independently processable chunk of a dataset. Partition size is the main lever on how well a workload parallelizes.