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There is a pdf file Data.pdf (~10 MB) stored in my Google Drive folder. I open the file in Adobe Reader, highlight a line and then save the file.

A re-sync will take place. I want to know whether the entire 10 MB of file will be synced or there exists a way by which changes can be synced by uploading only a part of the file?

SubCollector Bhadrachalam
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1 Answers1

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The feature you are asking is called "Block-Level File Copying". With this feature, when you make a change to a file, rather than copying the entire file from your hard drive to the cloud server again, only the parts of the file that changed (called the delta) get sent.

A Google Drive sync cannot be partial. If a small change is made to a large file, it redoes the entire file rather than just the change. Google Drive isn’t capable of doing block-level file copies.

As far as I know, among the best-known cloud providers, only Dropbox has this feature for all file types. Dropbox partitions every single file it stores into 4MB blocks. Each block is hashed with SHA-256 and a list of these hashes gets stored in what’s called a “blocklist” for reference.

This feature is also shared by OneDrive, which however only supports it for Microsoft Office documents.

For more information and some benchmarks, see the article
Block-Level File Copying and the Cloud.

harrymc
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    pcloud offers block level sync too: https://www.pcloud.com/help/drive-help-center/does-pcloud-support-block-level-sync – Haydentech Jul 22 '19 at 16:22
  • Since `blocklist` is considered for "Block-Level File Copying"; when a file is updated (a character is added at the beginning of the file), does Dropbox re-upload the complete file since the first block's hash will be change and it will also affect/change the hash of all the consequent blocks. @harrymc – alper Sep 29 '19 at 16:20
  • @alper: I suppose it will. – harrymc Sep 29 '19 at 16:37
  • As I understand since there is a case that whole file can be uploaded using "Block-Level File Copying", it creates duplication, could there be better approach to handle this, such as Git patches? @harrymc – alper Oct 02 '19 at 14:09
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    Are there any feature requests on this issue that you know of where we can vote and ask Google to add this? – aderchox Dec 04 '20 at 19:31