> I use a WebDAV server for storing backups (Fastmail Files). The server allows 10GB usage, but max file size is 250MB, *and in any case WebDAV does not support partial writes*. So writing a file requires reuploading it, which is the same situation as S3.
This is the part I absolutely missed. I was wondering how you were ensuring 1MB writes -- whether it was at the XFS level or mdraid level...
I think another thing that is missing which I'm inferring (hopefully correctly) is that you've mounted your webdav server to disk. So your stack is:
- LUKS
- mdraid
- losetup
- webdav fs mount
Is that correct?
>Ahh OK, I think I see -- since the block files are synced in full, you are always swapping blocks and doing ~1MB of writing no matter what.
Right. Let's say I update two files in the XFS layer. Those writes eventually result in three blocks in the lowest layer being modified. So now the `rclone sync` will need to do a `PUT` request to replace those three blocks on the WebDAV server, which means it'll upload 3MB of data to the server.