Re: [Duplicity-talk] Big bandwidth bill from Rackspace

[Nate Eldredge]

On Mon, 10 Jun 2013, Joseph D. Wagner wrote:

> On 06/10/2013 12:20 pm, address@hidden wrote:
> > yes. essentially it restores any file of the latest backup and compares
> > it to the original path in the local file system. therefore pretty much
> > all the last full and the incremental volumes have to be downloaded
> > again.
>
> Why does it need to download the entire file?  Why not just download a list 
> of files and their checksums (CRC32/64 or if paranoid SHA1/256/512)?  This 
> would minimize bandwidth usage for verify operations and be just as effective 
> as comparing the whole file.

This would tell you whether your local file had changed, but it wouldn't 
actually verify the backup.  Suppose some of the backup volumes are 
corrupted, but the signature / checksum files are intact.  Your proposal 
would not detect this.

I don't think there's any way to truly verify the backup other than 
fetching all the volumes, since we don't assume that we can run code or 
store encryption keys on the backend.

--
Nate Eldredge
address@hidden