Support

This is correct. Please take a look at http://stackoverflow.com/questions/26533245/the-authorization-mechanism-you-have-provided-is-not-supported-please-use-aws4

Unfortunately we can't use the V4 authentication API because it requires the entire content body to be signed. This would require the entire backup archive to be loaded to memory and processed. With part sizes over 512Kb (not a typo: five hundred and twelve KILOBYTES) this will always cause a memory or timeout issue.

At this time we don't have any solution. The solution is not up to us. It is a limit of what Amazon wants and what your servers can do. These two areas don't intersect. We can't do anything about it, sorry.

The past several days we have been refactoring the backup engine. While we were at this, I decided to try integrating the new Amazon SDK for PHP in it, which supports the AWS4 API with multipart uploads. Well, the Amazon SDK was buggy as far as multipart uploads are concerned, I patched it and now it does work. The next version of Akeeba Backup -which is currently in final testing- will have a new Amazon S3 post-processing engine which supports the new authentication API used in the Frankfurt and other newer S3 Regions.

The important thing to keep in mind is that using the AWS4 authentication scheme requires MUCH more memory than the old scheme. As a result you MUST have a PHP memory limit of at least 64Mb and you MUST either enable multipart uploads (which performs the upload in 5Mb pieces) or use a part size for split archives less than 5Mb. Just to give you an idea of peak memory consumption by the backup engine itself:

- Using the old AWS2 authentication scheme, single part 10Mb upload - 7.6Mb
- Using the new AWS4 authentication scheme, multipart 10Mb upload - 22Mb

The 12+ Mb difference using AWS4 can be attributed to the need to load each 5Mb upload chunk in memory twice, once to get an MD5 sum and once to upload to Amazon S3.

For what is worth, the new post-processing engine still supports using the old AWS2 authentication method for buckets created in old regions, such as Ireland, in case you have limited PHP memory available and don't wish to use a small part size for split archives.