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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. > I use a WebDAV s

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. > 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?

Arnavion 4y ago
The stack is XFS inside cryptsetup inside mdraid on top of losetup. The directory containing the losetup block files could be `rclone mount`'d from the WebDAV server, but that would make the setup unavailable if I didn't have network access. So instead I chose to have the block files in a regular directory, and I make sure to `rclone sync` that directory to the WebDAV server when I make changes in the XFS layer. Manually syncing also lets me run `sync` and watch the `rclone sync` output, which gives me greater confidence that all the layers have synced successfully. >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.
- hardwaresofton 4y ago
  Thanks for the explanation, this makes perfect sense now, didn't realize the syncing was manual/separate.

Arnavion 4y ago

The stack is XFS inside cryptsetup inside mdraid on top of losetup. The directory containing the losetup block files could be `rclone mount`'d from the WebDAV server, but that would make the setup unavailable if I didn't have network access. So instead I chose to have the block files in a regular directory, and I make sure to `rclone sync` that directory to the WebDAV server when I make changes in the XFS layer. Manually syncing also lets me run `sync` and watch the `rclone sync` output, which gives me greater confidence that all the layers have synced successfully. >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.

hardwaresofton 4y ago
Thanks for the explanation, this makes perfect sense now, didn't realize the syncing was manual/separate.