Re: [Xen-users] snapshot - backup for xen vm's

[Nico Kadel-Garcia <nkadel@xxxxxxxxx>]

Fajar A. Nugraha wrote:
> Nico Kadel-Garcia wrote:
>   
>
> > Mirror the whole RedHat DVD or network install site. Copy it to local
> > disk on the domain creating machine: you want this all to happen on
> > local disk, *NOT* over a network! Make a new partition, and mount it.
> > Copy the whole thing over to /var/cache/yum/base/packages and work
> > from there to install whatever you want, usually with yum. Do an
> > alternative root directory RPM or Yum installation into that
> > directory. But using yum, it downloads the files: it's vastly faster
> > to simply copy them over and use a "file:///" based URL, rather than
> > the classic HTTP or FTP URL's. be already available or wind up
> > downloaded into /var/cache/yum in the target directory, but you have a
> > huge advantage in being able to do the updates or add-on packages at
> > OS image install time, rather than wending your way through
> >
> >     
> In my setup I use a local yum repository via http.
> I have several installation methods, actually :
> - for PV domUs : use tar.gz templates.
> - for HVM domUs and physical machine : Use custom RH installer, either
> via CD/DVD or network (PXE) install.
>   
Working via HTTP is usually far, far slower than working via local file 
access to simply copy the repository.
It's even *faster* if you don't build your partition first, use "cp -al" 
to copy the repository to the chrooted /var/cache/yum/packages, and run 
a chrooted "yum clean all" when you'r edopne. Then you build the tarball 
from a directory, not a partition.
> The tar.gz fast is signifcantly faster than rpm-based install (including
> yum --installroot), even when the RPMS is on local disk (I tried this
> before), partly due to the fact that RPM needs extra steps (dep
> resolution, pre/post install scripts, etc.) other than simply writing
> files like the tar.gz. It has all necessary add-on packages included.
> You still need to do a "yum-upgrade" afterwards, but the total time
> required is still a lot faster.
>   
Oh, yes. I've done..... roughly 15,000 Linux servers in one month that 
way. I referred to the RPM/Yum games as ways of building your initial 
tarballs, without having to worry about a machine or environment to get 
that initial install into.
> The custom RH installer is basically the standard RHEL 5 installer with
> a kickstart file that adds additional yum repository and installs some
> local packages. It check files from CD/DVD (if available) and network
> repository, chooses the newest version, and performs the installation.
> This way it performs updates and installs add-on packages at OS image
> install time. The CD/DVD is created from an ISO image that is updated
> weekly to contain only the newest packages in addition to add-on
> packages. You still get newest packages at install time even if you use
> an old DVD since it will automatically compare the local version with
> the one on network repository and choose whichever is newest.
>   
Yup, I've used that sort of technique myself and highly approve of it. 
You do need to keep it vaguely up-to-date to keep installations fast: 
I've used it for network booting Beowulf clusters, which got wiped and 
re-installed every time they rebooted.
> Network BW is not an issue since I'm working on local, 1Gbps network.
> Besides, "Mirror the whole RedHat DVD or network install site. Copy it
> to local disk on the domain" would use up that BW anyway. Again, this
> was the best option for me but it might not be suitable for everybody.
>   
Nah, you leave it on a build machine from which you generate your 
tarballs, or do it on your HTTP server. The download directory is left 
around for the next session, not downloaded each time. It avoids the 
HTTP download time you mentioned above.
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