Quick answer
Fly.io documents persistent volume size as 1 GB default; 500 GB maximum. A volume can attach to only one Machine at a time.
Verified Aug 22, 2026Official source
Current limits
| Constraint | Current value | Scope | Verified source |
|---|---|---|---|
| persistent volume sizeA volume can attach to only one Machine at a time. | 1 GB default; 500 GB maximum | Per volume | Fly.ioAug 22, 2026 |
Why does this limit matter?
Horizontal application replicas need separate volumes or an external shared data service.
This value is scoped to Per volume; a different plan, runtime, model, endpoint, region, or account can produce a different effective constraint.
What should you check?
- Map each Machine to its volume and forecast capacity per replica.
- Confirm the exact plan, model, runtime, endpoint, region, and account that serve the failing workload.
- Record the observed value, response headers or configuration, timestamp, and source without logging secrets.
Important caveats
- Increasing a volume is straightforward, but shrinking requires migration to a new volume.
- Treat the official source and live account configuration as authoritative if they differ from this verified snapshot.
HyperObserve reports the documented platform constraint. Your application, SDK, gateway, provider, region, or account can impose a lower effective limit.
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