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    Object Storage Service:What do I do if the sizes of objects in the source and destination buckets are inconsistent after I configure mirroring-based back-to-origin?

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    Object Storage Service:What do I do if the sizes of objects in the source and destination buckets are inconsistent after I configure mirroring-based back-to-origin?

    Last Updated:Mar 20, 2026

    This issue occurs when Transfer queryString is not enabled in the mirroring-based back-to-origin configuration. Without it, OSS forwards requests to the origin without the query string — for example, without ?x-oss-process=image/resize,m_fill,h_250,w_400. The origin returns the full, unprocessed object instead of the processed version, so the object stored in the destination bucket is a different size than expected.

    Problem description

    After mirroring-based back-to-origin is configured, objects in the source and destination buckets have inconsistent sizes.

    Solution

    To diagnose and fix the issue:

    1. Access the same object from both buckets and compare the results. If the MD5 hash values differ, the object content is different.

      Note

      The following URLs are used in the examples:

      • Source: http://kowa-nXXXXXX1.oss-cn-xxxxxxx.aliyuncs.com/uploads/news/2018-03-06/AfmJWdArrx.jpg?x-oss-process=image/resize,m_fill,h_250,w_400

      • Destination: http://kowa-nXXXXXX2.oss-cn-xxxxxxx.aliyuncs.com/uploads/news/2018-03-06/AfmJWdArrx.jpg?x-oss-process=image/resize,m_fill,h_250,w_400

    2. In your mirroring-based back-to-origin configuration, confirm that Transfer queryString is selected.

    3. Verify the fix by accessing the object for the first time using the query string. The first time you use http://kowa-nXXXXXX2.oss-cn-xxxxxxx.aliyuncs.com/uploads/news/2018-03-06/AfmJWdArrx.jpg?x-oss-process=image/resize,m_fill,h_60,w_80 to access the object in the destination bucket, back-to-origin is triggered and the source bucket returns the result of image processing to the destination bucket. The sizes of objects in both buckets should now be the same.

      • Source: http://kowa-nXXXXXX1.oss-cn-xxxxxxx.aliyuncs.com/uploads/news/2018-03-06/AfmJWdArrx.jpg?x-oss-process=image/resize,m_fill,h_60,w_80

      • Destination: http://kowa-nXXXXXX2.oss-cn-xxxxxxx.aliyuncs.com/uploads/news/2018-03-06/AfmJWdArrx.jpg