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LVM snapshots on 2.6.8-022stab064.1-enterprise [message #1740]

Tue, 21 February 2006 20:34

crackez
Messages: 3
Registered: February 2006
Location: Philadelphia Area

Junior Member

I have a nice 4 way box with 5GB of RAM running CentOS 4.2/OpenVZ. I like it a lot, but I've come across a stumbling block: Backups.

I want to make snapshots and dump them over the network to a disk cache before being dumped to tape.

I generally do this with lvm snapshots, the dump command, and ssh, but when I try to create the lvm snapshot, I get an error.

# lvcreate -s -l 20 snap_root /dev/vg_sys/root
  snapshot: Required device-mapper target(s) not detected in your kernel
  lvcreate: Create a logical volume
...
# modprobe dm_snapshot
FATAL: Module dm_snapshot not found.

Are lvm snapshots unavailable on the openvz kernels?

--Andy

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Re: LVM snapshots on 2.6.8-022stab064.1-enterprise [message #1744 is a reply to message #1740]

Tue, 21 February 2006 23:24

curx
Messages: 739
Registered: February 2006
Location: Nürnberg, Germany

Senior Member

Hi Andy,

# CONFIG_DM_SNAPSHOT is not set

You must build your own kernel with enabled lvm/snapshot targets!

Thorsten

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Re: LVM snapshots on 2.6.8-022stab064.1-enterprise [message #1775 is a reply to message #1744]

Thu, 23 February 2006 14:32

crackez
Messages: 3
Registered: February 2006
Location: Philadelphia Area

Junior Member

Is there any reason the binary OpenVZ kernels don't come with CONFIG_DM_SNAPSHOT enabled?

Just curious.

--Andy

[Updated on: Thu, 23 February 2006 14:37]

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Re: LVM snapshots on 2.6.8-022stab064.1-enterprise [message #1782 is a reply to message #1775]

Thu, 23 February 2006 20:08

dev
Messages: 1693
Registered: September 2005
Location: Moscow

Senior Member

there is no any real reason for this i suppose.
if someone will report that it works and disered to have, I will turn it on. Not a problem.

http://static.openvz.org/userbars/openvz-developer.png

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Re: LVM snapshots on 2.6.8-022stab064.1-enterprise [message #1795 is a reply to message #1740]

Fri, 24 February 2006 19:30

crackez
Messages: 3
Registered: February 2006
Location: Philadelphia Area

Junior Member

I was able to get lvm snapshots working.
I tested it with ovzkernel-2.6.8-022stab070.1.src.rpm, changed one line in the enterprise config (CONFIG_DM_SNAPSHOT=y), and rebuilt.

rpm -ivh ovzkernel-2.6.8-022stab070.1.src.rpm
# make changes to config - set CONFIG_DM_SNAPSHOT=y
vim /usr/src/redhat/SOURCES/kernel-2.6.8-022stab070-i686-enterprise.config.ovz
rpmbuild -bb --target=i686 /usr/src/redhat/SPECS/kernel-ovz.spec
# wait a little while
rpm -ivh /usr/src/redhat/RPMS/i686/ovzkernel-enterprise-2.6.8-022stab070.1.i686.rpm
reboot

Snapshots seem to be working fine with the new build.

# lvcreate -s -l 20 -n snap_vz vg_sys/vz
  Logical volume "snap_vz" created
# lvremove -f vg_sys/snap_vz
  Logical volume "snap_vz" successfully removed

Hope this helps.

--Andy

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