Xen users - Feb 2007 - what to backup Xen partition with?

Hi all,
I choosed to install my domUs on separate partitions.
All are "full virtualized" domUs.
I have 4 x 10GB to backup. Of course, the backup is done while the domains are 
down.
The domains are 4 different Linux distributions I make tests on.
I might  brake some, and dont want to go more time thrgouh the install 
process: I just want, if I brake the domU system, to just overwrite the 
partition with the last known good configuration.
For the moment, the idea I apply is to "dd" the partition to a file
and then
bzip2 it. for a first install, It goes from 10GB to 1GB (more or less, 
depends on the distro).
But it''s still too slow (dd+bzip2). Would you know another way to make 
partition backups?

thank you

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On Thursday 01 February 2007, Rakotomandimby (R12y) Mihamina
wrote:
> But it''s still too slow (dd+bzip2). Would you know another way to
make
> partition backups?
if you were using LVM instead of partitions, you could do a snapshot, and then 
use the partition-on-block-device tools to mount it (ntfs? ro?) and then use 
rsync to backup only modified files.

but since you can''t do a snapshot, i''d use rsync over ssh
(''-c blowfish-cbc''
makes ssh easier on the CPU!) to copy from a running DomU


-- 
Javier


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> I have 4 x 10GB to backup. Of course, the backup is done 
> while the domains are down.
> The domains are 4 different Linux distributions I make tests on.
[...]
> But it''s still too slow (dd+bzip2). Would you know another 
> way to make partition backups?
Hi.

Since these are all Linux distros, AND you are backing up while the
domains are down, I would suggest that you simply mount the partitions
and do a tarball of the file system - or do an rsync of the whole thing
for even better performance.

Cheers
-- Jan Holst Jensen, Denmark

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JHJE (Jan Holst Jensen) wrote:
>> I have 4 x 10GB to backup. Of course, the backup is done 
>> while the domains are down.
>> The domains are 4 different Linux distributions I make tests on.
>>     
> [...]
>   
>> But it''s still too slow (dd+bzip2). Would you know another 
>> way to make partition backups?
>>     
>
> Hi.
>
> Since these are all Linux distros, AND you are backing up while the
> domains are down, I would suggest that you simply mount the partitions
> and do a tarball of the file system - or do an rsync of the whole thing
> for even better performance.
>   
dd will always be slow and oversized! You have to read every single 
byte, and if you''re writing to a file on the same disk, the disk is 
going to be chugging back and forth even worse. Even on another disk, 
it''s hardly efficient. And if it''s a live file system,
you''re in danger
because it''s possible, even likely that blocks will not yet be written 
to disk and you can have an extremely corrupt filesystem recorded 
without the information to fix it.

So don''t do partition backups. Store a note about the size and location
of the partition, a note about the type of file system, then mount it 
and do a tarball of the files. There are techniques to make a 
file-system snapshot and a "paused" copy of the Xen domain that may
also
help: snapshot it and build a new domaiun frm the copy, then shut the 
copy down and make a tarball from *that*. It''ll also restore to a new 
partition a lot faster than a dd copy, and you can use a different sized 
partition for the newly restored domain if desired.

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Rakotomandimby (R12y) Mihamina <mihamina.rakotomandimby <at> 
etu.univ-orleans.fr> writes:
> 
> Hi all,
> I choosed to install my domUs on separate partitions.
> All are "full virtualized" domUs.
> I have 4 x 10GB to backup. Of course, the backup is done while the domains 
are 
> down.
> The domains are 4 different Linux distributions I make tests on.
> I might  brake some, and dont want to go more time thrgouh the install 
> process: I just want, if I brake the domU system, to just overwrite the 
> partition with the last known good configuration.
> For the moment, the idea I apply is to "dd" the partition to a
file and then
> bzip2 it. for a first install, It goes from 10GB to 1GB (more or less, 
> depends on the distro).
> But it''s still too slow (dd+bzip2). Would you know another way to
make
> partition backups?
> 
> thank you
> 
It''s not goign to be of any great help now, but LVM is very handy.  I
run all
my domU''s in LVM which enables you to make snaphots of your partitions.

http://tldp.org/HOWTO/LVM-HOWTO/
http://www.cl.cam.ac.uk/research/srg/netos/xen/readmes/user/user.html#SECTION03330000000000000000

Cheers,




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On Friday 02 February 2007 08:23, Nico Kadel-Garcia
wrote:
> So don''t do partition backups. Store a note about the size and
location
> of the partition, a note about the type of file system, then mount it
> and do a tarball of the files. There are techniques to make a
> file-system snapshot and a "paused" copy of the Xen domain that
may also
> help: snapshot it and build a new domaiun frm the copy, then shut the
> copy down and make a tarball from *that*. It''ll also restore to a
new
> partition a lot faster than a dd copy, and you can use a different sized
> partition for the newly restored domain if desired.
I put /dev/sda7 as /dev/hda of the domU
The domU has only one partition (/dev/hda1), 
When, from the dom0, I try to mount /dev/sda7, the filesystem is not known.
I cannot mount it in order to back it up...

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On 2 Feb 2007 at 20:45, Rakotomandimby (R12y) Mihamina wrote:
> On Friday 02 February 2007 08:23, Nico Kadel-Garcia wrote:
> > So don''t do partition backups. Store a note about the size
and location
> > of the partition, a note about the type of file system, then mount it
> > and do a tarball of the files. There are techniques to make a
> > file-system snapshot and a "paused" copy of the Xen domain
that may also
> > help: snapshot it and build a new domaiun frm the copy, then shut the
> > copy down and make a tarball from *that*. It''ll also restore
to a new
> > partition a lot faster than a dd copy, and you can use a different
sized
> > partition for the newly restored domain if desired.
> 
> I put /dev/sda7 as /dev/hda of the domU
> The domU has only one partition (/dev/hda1), 
> When, from the dom0, I try to mount /dev/sda7, the filesystem is not known.
> I cannot mount it in order to back it up...
"man kpartx", or serch the list for "kpartx" and
"mount".

Ulrich


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