Object Storage Service:How do I upload large objects to OSS?

OSS supports objects from 0 bytes to 48.8 TB. For objects larger than 5 GB, simple upload, form upload, and append upload are not supported. Use multipart upload, resumable upload, ossbrowser, or ossutil instead.

Upload methods

OSS supports objects from 0 bytes to 48.8 TB. Alternative upload methods are useful in the following scenarios:

• The object is larger than 5 GB. The OSS console, simple upload, form upload, and append upload do not support objects above this limit.

• The object is smaller than 5 GB, but intermittent timeouts or connection drops occur due to poor network performance.

Choose an upload method

Method 1: Multipart upload or resumable upload

Multipart upload and resumable upload are well suited for:

• Objects larger than 5 GB: PutObject does not support objects above this limit.

• Streaming uploads: Start uploading before the final object size is known — for example, in cloud video recording or video surveillance applications.

• Unreliable networks: Resumable upload retries only the failed parts, not the entire object. This is especially efficient when uploads are frequently interrupted.

• Parallel upload acceleration: Split a large object into parts and upload them concurrently to maximize throughput.

For more information, see Multipart upload and Resumable upload.

Method 2: ossbrowser

ossbrowser uses multipart upload and resumable upload by default, supporting objects up to 48.8 TB. Keep the following in mind:

• Log on with a Security Token Service (STS) token, or use the AccessKey pair of a RAM user.

• To use the simple policy feature, log on with the AccessKey pair of a RAM user who has RAM configuration permissions.

• When many uploads or downloads run simultaneously, reduce the concurrency limit to improve the speed of a specific task.

• The maximum supported object size is 48.8 TB.

For more information, see Common operations.

Method 3: ossutil

Use the cp command to upload large objects. ossutil provides fine-grained control over resumable upload and concurrency:

• Use the cp command to upload large objects.

• Set --bigfile-threshold to define the object size above which resumable upload is used automatically.

• Set -jobs and -parallel to control the number of concurrent upload tasks when uploading one or more large objects.

• For batch uploads of many objects, use ossutil together with ossimport.

• For smaller batches, ossutil alone is sufficient.

For more information, see cp (upload files).

Troubleshooting

• PutObject fails when uploading large objects. Common causes:

  • The object exceeds 5 GB. PutObject does not support objects larger than 5 GB. Use ossutil to upload the object in parts.

  • PutObject times out with no response. A large maximum transmission unit (MTU) value can cause this. Run netstat -i on the Elastic Compute Service (ECS) instance to check the current MTU. The default MTU for internal and external network interface cards is 1500.

    • Lower the MTU. For example, run ip link set dev eth0 mtu 1470 on Linux to set the MTU for eth0 to 1470.

    • Switch to the MultipartUpload operation or ossutil.

• A large object cannot be uploaded in parts concurrently. To enable concurrent part uploads:

  • With ossutil: specify --bigfile-threshold, -jobs, and -parallel to control concurrency.

  • With OSS APIs or SDKs: use the MultipartUpload operation and write concurrent upload logic. Many SDKs expose a concurrency parameter — for example, taskNum in OSS SDK for Java and num_threads in OSS SDK for Python.