Hi,
i have some virtual machines running on logical volumes formatted with OCFS2.
I'd like to snapshot the running guests
to backup them easily afterwards. The files of the guests are big (100 - 300GB),
but the content changes only slowly.
So i thought that rsync would be a great benefit because it justs transfers the
difference between the current file and
the one backuped one day before. I was wrong.
Some more information:
The file which hosts the disk from the vm is a dynamic one, that means it grows
with the need from the guest os, up to a limit.
While creating the guest the file is not completely allocated, although "ls
-la" shows already the maximum size.
The snapshot OCFS2 creates (in Oracle terms a reflink) has immediately after
creation also the maximum size.
Indeed it allocates at the creation no disk space, and grows with changes in the
source file (COW).
A reflink shares in the beginning the sectors with the source file.
Just to illustrate:
ha-idg-1:/cluster/guests/servers_alive # ls -ls
total 47409860
0 drwxr-xr-x 2 root root 3896 Mar 13 13:25 lost+found
47409860 -rwxr-xr-x 1 root root 107374182400 Mar 14 10:57 sa.raw
ha-idg-1:/cluster/guests/servers_alive # reflink -v sa.raw sa.raw.snap
`sa.raw.snap' => `sa.raw'
ha-idg-1:/cluster/guests/servers_alive # ll
total 94820568
drwxr-xr-x 2 root root 3896 Mar 13 13:25 lost+found
-rwxr-xr-x 1 root root 107374182400 Mar 14 11:37 sa.raw
-rwxr-xr-x 1 root root 107374182400 Mar 14 11:37 sa.raw.snap
ha-idg-1:/cluster/guests/servers_alive # ls -li
total 94837904
558594 drwxr-xr-x 2 root root 3896 Mar 13 13:25 lost+found
558595 -rwxr-xr-x 1 root root 107374182400 Mar 14 13:36 sa.raw
558596 -rwxr-xr-x 1 root root 107374182400 Mar 14 11:37 sa.raw.snap
ha-idg-1:/cluster/guests/servers_alive # ls -ls
total 94837904
0 drwxr-xr-x 2 root root 3896 Mar 13 13:25 lost+found
47427620 -rwxr-xr-x 1 root root 107374182400 Mar 14 13:36 sa.raw
47410284 -rwxr-xr-x 1 root root 107374182400 Mar 14 11:37 sa.raw.snap
ha-idg-1:/cluster/guests/servers_alive # df -h
Filesystem Size Used Avail Use% Mounted on
...
/dev/dm-9 115G 49G 67G 42% /cluster/guests/servers_alive
You see that just 49GB are allocated, because the source has not grown to the
maximum, and the reflink occupies no space
in the beginning. Maximum size is 100GB.
I would now expect a rsync from the snap would transfer just some megay bytes to
the file from the day before.
But it doesn't:
ha-idg-1:/cluster/guests/servers_alive # time rsync -av --stats sa.raw.snap
/mnt/idg-2/SysAdmin_AG_Wurst/backup/cluster/test
sending incremental file list
sa.raw.snap
Number of files: 1
Number of files transferred: 1
Total file size: 107374182400 bytes
Total transferred file size: 107374182400 bytes
Literal data: 107374182400 bytes
Matched data: 0 bytes
File list size: 29
File list generation time: 0.001 seconds
File list transfer time: 0.000 seconds
Total bytes sent: 107387289677
Total bytes received: 31
sent 107387289677 bytes received 31 bytes 98385056.99 bytes/sec
total size is 107374182400 speedup is 1.00
real 18m10.879s
user 10m48.205s
sys 7m2.250s
It transfers the complete file. I'm i doing something wrong or is the
desired behviour not possible ?
Bernd
--
Bernd Lentes
Systemadministration
Institut für Entwicklungsgenetik
Gebäude 35.34 - Raum 208
HelmholtzZentrum münchen
[ mailto:bernd.lentes at helmholtz-muenchen.de | bernd.lentes at
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 14 Mar 2018, Lentes, Bernd via rsync wrote:> I would now expect a rsync from the snap would transfer just some megay > bytes to the file from the day before. > But it doesn't: > > ha-idg-1:/cluster/guests/servers_alive # time rsync -av --stats > sa.raw.snap /mnt/idg-2/SysAdmin_AG_Wurst/backup/cluster/testHi Bernd, When doing rsync locally, diff alg is not involved, this is why file is fully transferred. Ben
no backup - no mercy ----- On Mar 14, 2018, at 2:19 PM, Ben RUBSON ben.rubson at gmail.com wrote:> On 14 Mar 2018, Lentes, Bernd via rsync wrote: > >> I would now expect a rsync from the snap would transfer just some megay >> bytes to the file from the day before. >> But it doesn't: >> >> ha-idg-1:/cluster/guests/servers_alive # time rsync -av --stats >> sa.raw.snap /mnt/idg-2/SysAdmin_AG_Wurst/backup/cluster/test > > Hi Bernd, > > When doing rsync locally, diff alg is not involved, this is why file is > fully transferred. > > BenHi Ben, also when the target is a cifs share, it's still considered as local ? Is there something i can do to get the diff algorithm used ? Copying via ssh to the cifs server is unfortunately not possible. 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