RE: [Xen-users] Re: cow implementation

["Petersson, Mats" <mats.petersson@xxxxxxx>]

 

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From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Anand
Sent: 10 January 2006 11:59
To: Molle Bestefich
Cc: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] Re: cow implementation

Thanks for the reply. And for the filesystem are you using flat images or volumes ?

Isn't tar and gzip combination going to be a cpu hog ? 

Gzip will use up a fair amount of cpu-time, but the time it take to transfer the image that is 30-70% smaller is significantly more than the CPU-time it's taken, so unless you have something else productive to do with your cpu whilst you're backing up/transferring the file(s), you're probably better off compressing the file(s).  
 

--

Mats 

On 1/10/06, Molle Bestefich <molle.bestefich@xxxxxxxxx> wrote:

Anand wrote:
> > > What are you using then ?
> >
> > Uhm, tar+gzip and a differ for now :-)...
> >
> > I'll admit it's far from optimal :-).
>
> huh ? i have to say it just went over my head.
> Care to fly a little low so i can understand something about it ? ;)

I make a tar archive of each domU filesystem:
# tar /backup/domain1_`date +%s`.tar /{bin,sbin,etc,home,lib,opt,usr,var}

Then gzip it.

I'm experimenting with various binary differs so I can diff the backup
locally on the server against the previous backup .tar.gz and only
send the couple of MB that actually changed to my backup server.  The
backups I've made in the past worked by sending the entire .tar.gz,
which is a couple GB each, which was sort of inefficient.

--

regards,

Anand

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