[DRBD-user] DRBD and KVM for a HA-Cluster ?

Felix Frank ff at mpexnet.de
Fri Jan 14 17:49:13 CET 2011

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.

On 01/14/2011 05:39 PM, Lentes, Bernd wrote:
> Felix Frank wrote:
>>> Ok, i try to unnderstand:
>>> With lvcreate -s i create the snapshot. This creates an 
>> entry /dev/vgxxx/lvxxx.
>>> Then i use kpartx for ... what ? Creating a second entry in 
>> /dev/... ?
>>> I tested this:
>>> created a snapshot /dev/vg1/lv_home_snapshot.
>>> kpartx -lv  /dev/vg1/lv_home_snapshot says ... nothing.
>> "lv_home_snapshot"? Is that an LV that contains a partitioned 
>> disk image?
>> If it is, it's not clear to me why no partitions are 
>> displayed. I've used this with an image of a VM harddrive before.
>> Sorry to be not quite helpful.
> lv_home_snapshot is a snapshot form a normal LV which has a filesystem.
> My question is: I like to install vm's using KVM into plain lv's which have no filesystem.
> How can i backup a partition which has no filesystem without using dd ? DD is slow and copies _every_
> sector of a 50GB lv, although just e.g. 20GB are occupied.

Do it using kpartx. I thought that much was obvious from my previous
response. Please read it up.

No, it's not supposed to work with single partitions. It works with
partitioned drives/images. That's what you need. You need no tool that
helps you with a single partition containing a filesystem. You want
nodes for the partitions contained in a block device (your LV snapshot)
that represents a partitioned disk.

Test it with the kind of block device you actually need to interact
with, not some random LV you've got lying around.

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