Backup Failures on Large Installations – MinIO Multipart-Upload Limit

[CBCUN]

Hello everyone,

I ran into an issue with a large Cloudron/Box installation where the backup aborts with this log entry:

… Upload progress: {"loaded":104878571520,"part":10002,…}
BoxError: backuptask exited with code 1
reason: “Internal Error”

Investigation
• Both AWS S3 and MinIO enforce a maximum of 10,000 parts per multipart upload.
• Default part size in Cloudron/Box is 10 MB → max transferable per upload ≈ 100 GB (10 000 × 10 MB).
• In my case part number 10 002 was attempted → limit exceeded → upload aborted.

Part Size vs. Maximum Backup Size

Part Size	Max Parts	Max Data Volume
10 MB	10 000	100 GB
50 MB	10 000	500 GB
100 MB	10 000	1 000 GB
150 MB	10 000	1 500 GB

Solution: Increase Part Size
This reduces the number of parts and allows backups up to ~500 GB without hitting the multipart limit.

Sources
• AWS S3 Multipart-Upload Overview: https://docs.aws.amazon.com/AmazonS3/latest/userguide/mpuoverview.html
• MinIO Limits (10 000 parts, part size 5 MiB–5 TiB): https://github.com/minio/minio/blob/master/docs/minio-limits.md

Greetings
Christian

[joseph]

If you want to increaes the part size, it's in Backups -> Configure -> Advanced . The suggestion solution does not seem correct as @BrutalBirdie pointed out

[BrutalBirdie]

@CBCUN said in Backup Failures on Large Installations – MinIO Multipart-Upload Limit:

Run in your Cloudron/Box environment:

export CLOUDRON_BACKUP_S3_PART_SIZE=50mb

Could you follow up on that with a bit more explanation?

Run in your Cloudron/Box environment so ssh into the server and as root just export CLOUDRON_BACKUP_S3_PART_SIZE=50mb?
This sounds wrong
So could you please provide a more in depth guide, that be awesome!

[joseph]

If you want to increaes the part size, it's in Backups -> Configure -> Advanced . The suggestion solution does not seem correct as @BrutalBirdie pointed out

[CBCUN]

Yes, can be solved. Just for others with this kind of problem.