Re: [rdiff-backup-users] Re: Remote encrypted backup with slow connection.

[Piotr Karbowski]

On Mon, Sep 21, 2009 at 8:21 PM, Dominic Raferd <address@hidden> wrote:
> Piotr Karbowski wrote:
>>
>> On Mon, Sep 21, 2009 at 2:02 PM, Matthew Miller <address@hidden> wrote:
>>
>>>
>>> On Mon, Sep 21, 2009 at 01:58:11PM +0200, Piotr Karbowski wrote:
>>>
>>>>
>>>> local rdiff-backup dir with remote server but how? If I will use for
>>>> example rsync it still need to check whole files for changes (read,
>>>> download it) and upload only new. I hope you will understand what I
>>>> need and help me.
>>>>
>>>
>>> rsync won't check whole files unless you give the -c flag. Otherwise, it
>>> just compares metadata. I don't know if that's also the case with
>>> rdiff-backup, but I assume so.
>>>
>>
>> So I need to know how rdiff default compares data, if by size and
>> mod-time, it will not be so painful but still itefficient  will download 
>> changed
>> files to generate diff.
>
> Rdiff-backup is designed to be ultra-efficient at this activity. It only
> sends the changes in a file over the wire, not the whole file. To do this it
> uses the librsync library which is effectively the same as rsync. You can
> read more about the technique at http://en.wikipedia.org/wiki/Rsync.
> rdiff-backup does not use file times to determine whether to do backups. It
> can backup very large files with small changes very quickly.
>
> Dominic
>

You dont understand me, rdiff-backup is efficient, but to make diff it
must read WHOLE file, on remote nfs or sshfs it is SLOOOOW and
painful.