Hello Adam,
The Megaupload did a scan with a percentage of the uploaded file. I do not know how, but you sent a 1GB file and in a few minutes, he gave as the upload completes. At the time I did a test by sending a single file, it took eight hours. The next day I went to send the same file and sent it in 22 minutes.
It's impossible to do a check with a piece of the file?
If not, even if the file is to be sent, we can not do the hash to avoid overuse in storage? The most expensive part of storage as it is not in Internet bandwidth, the capacity of the disk or in the storage means.
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I have an idea.
How about making a hash on the file and store the result in the database? So the next before being stored files (even in temp dir) shows the name, the hash value and size. If equal, no store, just direct a noma download URL for the file already exists.
This new technology does not seem very hard to develop and will raise much intelligence program.
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Best Regards