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

Felix Frank ff at mpexnet.de
Sat Jan 15 00:50:57 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.


> Frank, your idea is that the lv (and also the snapshot) contains one or more partitions, depending on the guest OS setup.

It's "Felix".

> For these partitions, i create nodes in /dev using kpartx -a /dev/vgxxx/vm_snapshot.
> These nodes can now be mounted. Now my backup software in the host (Legato Networker client) is able to save the partitions of my guest, right ?
> Is that your idea ?


> Two questions:
> 1. Are you sure that kpartx is able to read the raw data written by KVM into the lv's, that it is able to recognize the partitions ?

It's what it does. Try it, I can't hand out guarantees ;p

> 2. What is if my guest OS contains lv's, not only physical partitions ?

You mean, your guest created PVs atop its own partitions inside your 
dedicated guest LV?

Good question, you will have to vgscan or pvscan for them or something 
along those lines. I'm not sure how well that will work.

The bottom line is that you get /dev/mapper/vg_snapshot-part* as 
ordinary block devices that you can treat like any other plain old 
partition. If one or more of them are PVs, treat them like they are. 
Whatever that implies in this use case.

But I can conceivably see that being somewhat problematic, yes. If in 
doubt, just avoid LVM inside your guests ;)


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