Subject: Re: [vserver] Hashify and efficient cross-server copying
From: Gordan Bobic <gordan@bobich.net>
Date: Thu, 26 Aug 2010 11:25:15 +0100

On 08/26/2010 11:14 AM, Jeff Jansen wrote:
> Gordan Bobic<gordan@bobich.net>  wrote on 2010-Aug-26:
>> Is there an efficient way to copy hashified data across hosts? e.g.
>> using tar or rsync?
>>
>> I want to have a backup host that I can periodically rsync data to, but
>> would like to avoid having to re-hashify the files at the destination
>> since they will already be hashified at source.
>
> If you rsync the directory where your vservers all "live" and include the "-H"
> switch, then rsync will create the hard links on the target side.
>
> Something like:
>
> rsync -avH --delete --numeric_ids /vservers/ target:/vservers/

Indeed, I thought of that, but my concern is about these then not being 
marked COW. Would re-hashifying rectify this correctly or would it 
assume that since the files are already hard-linked it is deliberate and 
that it should leave them alone? And would this be as cheap in terms of 
disk I/O as writing the COW flag to the affected files?

Gordan