The VAST cluster handles the object's Entity Tag (ETag) field as follows:
For regular uploads (non-multipart):
The ETag returned by the VAST cluster is the checksum of data in the upload request.
For multipart uploads:
For each part being uploaded, a separate ETag is returned as a header in the response. The VAST cluster expects each subsequent part upload request to include the ETag and the part number of the previous part upload request. Thus all parts of the multipart upload will have their own ETags generated at the part's upload time. Once the multipart upload is complete and all parts are consolidated, the VAST cluster generates a single ETag for the whole multipart upload by calculating a checksum of the parts' ETags.