libvirt users - Mar 2018 - Re: snapshot with libvirt tools or with lvm tools ?

Hi,

i asked already a time ago about snapshots. I have some guests, each resides in
a raw file, placed on an ext3 fs which is on top of a logical volume, for each
guest a dedicated lv.
The raw is not a "must have", if there are obvious reasons i can
convert them to a qcow2.
What i want is a consistent backup of each guest taken overnight. If possible i
won't have downtime.
I can use the libvirt tools, but the lvm way seems to be more elegant. 
Before copying the file the guests resides in i take a snapshot from the
respective lv. Then i mount the snapshot and transfer it via rsync on a CIFS
share.
Rsync seems to be the appropriate tool because i just transfer the changes in
the file compared to the file from a day before. So i don't have to transfer
complete and big raw files but just the difference.

The guest still can be running, and after the transfer of the snapshot file i
just delete it, and the next night the same procedure.

What do you think ?

Bernd

-- 

Bernd Lentes 
Systemadministration 
Institut für Entwicklungsgenetik 
Gebäude 35.34 - Raum 208 
HelmholtzZentrum münchen 
[ mailto:bernd.lentes@helmholtz-muenchen.de | bernd.lentes@helmholtz-muenchen.de
]
phone: +49 89 3187 1241 
fax: +49 89 3187 2294 
[ http://www.helmholtz-muenchen.de/idg | http://www.helmholtz-muenchen.de/idg ] 

no backup - no mercy
 

Helmholtz Zentrum Muenchen
Deutsches Forschungszentrum fuer Gesundheit und Umwelt (GmbH)
Ingolstaedter Landstr. 1
85764 Neuherberg
www.helmholtz-muenchen.de
Aufsichtsratsvorsitzende: MinDir'in Baerbel Brumme-Bothe
Geschaeftsfuehrer: Prof. Dr. Guenther Wess, Heinrich Bassler, Dr. Alfons Enhsen
Registergericht: Amtsgericht Muenchen HRB 6466
USt-IdNr: DE 129521671

----- On Mar 9, 2018, at 4:39 PM, Bernd Lentes
bernd.lentes@helmholtz-muenchen.de wrote:
> Hi,
> 
> i asked already a time ago about snapshots. I have some guests, each
resides in
> a raw file, placed on an ext3 fs which is on top of a logical volume, for
each
> guest a dedicated lv.
> The raw is not a "must have", if there are obvious reasons i can
convert them to
> a qcow2.
> What i want is a consistent backup of each guest taken overnight. If
possible i
> won't have downtime.
> I can use the libvirt tools, but the lvm way seems to be more elegant.
> Before copying the file the guests resides in i take a snapshot from the
> respective lv. Then i mount the snapshot and transfer it via rsync on a
CIFS
> share.
> Rsync seems to be the appropriate tool because i just transfer the changes
in
> the file compared to the file from a day before. So i don't have to
transfer
> complete and big raw files but just the difference.
> 
> The guest still can be running, and after the transfer of the snapshot file
i
> just delete it, and the next night the same procedure.
> 
> What do you think ?
> 
It does not work as expected :-(
My lv's are clustered, but snapshotting a clustered lv requires to activate
the source lv exclusively on one node, which is not possible when it's
mounted and files on it are open.
So i have to try it with libvirt and qemu.
I'd like to create the snapshot while running the guest, take the backup,
and merge (or commit) the changes after the copy procedure, still with a running
guest.
Is there  a way to do this ? I found
https://wiki.libvirt.org/page/Live-disk-backup-with-active-blockcommit , but my
software seems to be too old:
I have libvirt-1.2.5-23.3.1. But my virsh offers blockcommit:

virsh # help blockcommit
  NAME
    blockcommit - Start a block commit operation.

  SYNOPSIS
    blockcommit <domain> <path> [<bandwidth>] [<base>]
[--shallow] [<top>] [--delete] [--wait] [--verbose] [--timeout
<number>] [--async]

  DESCRIPTION
    Commit changes from a snapshot down to its backing image.

  OPTIONS
    [--domain] <string>  domain name, id or uuid
    [--path] <string>  fully-qualified path of disk
    [--bandwidth] <string>  bandwidth limit in MiB/s
    [--base] <string>  path of base file to commit into (default bottom of
chain)
    --shallow        use backing file of top as base
    [--top] <string>  path of top file to commit from (default top of
chain)
    --delete         delete files that were successfully committed
    --wait           wait for job to complete
    --verbose        with --wait, display the progress
    --timeout <number>  with --wait, abort if copy exceeds timeout (in
seconds)
    --async          with --wait, don't wait for cancel to finish

But it doesn't work ? Although help offers it ?

Bernd
 

Helmholtz Zentrum Muenchen
Deutsches Forschungszentrum fuer Gesundheit und Umwelt (GmbH)
Ingolstaedter Landstr. 1
85764 Neuherberg
www.helmholtz-muenchen.de
Aufsichtsratsvorsitzende: MinDir'in Baerbel Brumme-Bothe
Geschaeftsfuehrer: Prof. Dr. Guenther Wess, Heinrich Bassler, Dr. Alfons Enhsen
Registergericht: Amtsgericht Muenchen HRB 6466
USt-IdNr: DE 129521671

----- On Mar 9, 2018, at 7:05 PM, Bernd Lentes
bernd.lentes@helmholtz-muenchen.de wrote:

> 
> It does not work as expected :-(
> My lv's are clustered, but snapshotting a clustered lv requires to
activate the
> source lv exclusively on one node, which is not possible when it's
mounted and
> files on it are open.
> So i have to try it with libvirt and qemu.
> I'd like to create the snapshot while running the guest, take the
backup, and
> merge (or commit) the changes after the copy procedure, still with a
running
> guest.
> Is there  a way to do this ? I found
> https://wiki.libvirt.org/page/Live-disk-backup-with-active-blockcommit ,
but my
> software seems to be too old:
> I have libvirt-1.2.5-23.3.1. But my virsh offers blockcommit:
> 
> virsh # help blockcommit
>  NAME
>    blockcommit - Start a block commit operation.
> 
>  SYNOPSIS
>    blockcommit <domain> <path> [<bandwidth>]
[<base>] [--shallow] [<top>]
>    [--delete] [--wait] [--verbose] [--timeout <number>] [--async]
> 
>  DESCRIPTION
>    Commit changes from a snapshot down to its backing image.
> 
>  OPTIONS
>    [--domain] <string>  domain name, id or uuid
>    [--path] <string>  fully-qualified path of disk
>    [--bandwidth] <string>  bandwidth limit in MiB/s
>    [--base] <string>  path of base file to commit into (default
bottom of chain)
>    --shallow        use backing file of top as base
>    [--top] <string>  path of top file to commit from (default top of
chain)
>    --delete         delete files that were successfully committed
>    --wait           wait for job to complete
>    --verbose        with --wait, display the progress
>    --timeout <number>  with --wait, abort if copy exceeds timeout (in
seconds)
>    --async          with --wait, don't wait for cancel to finish
> 
> But it doesn't work ? Although help offers it ?
> 
> Bernd
> 
Hmm,

it seems i really have a version too old. This is what i get:

virsh # blockcommit windows7x64 /cluster/guests/servers_alive/sa_snap.qcow2
--wait --verbose
error: Operation not supported: committing the active layer not supported yet

Is there no way to achieve what i want ?


Bernd
 

Helmholtz Zentrum Muenchen
Deutsches Forschungszentrum fuer Gesundheit und Umwelt (GmbH)
Ingolstaedter Landstr. 1
85764 Neuherberg
www.helmholtz-muenchen.de
Aufsichtsratsvorsitzende: MinDir'in Baerbel Brumme-Bothe
Geschaeftsfuehrer: Prof. Dr. Guenther Wess, Heinrich Bassler, Dr. Alfons Enhsen
Registergericht: Amtsgericht Muenchen HRB 6466
USt-IdNr: DE 129521671