[DRBD-user] DRBD inside KVM virtual machine

Nick Morrison nick at nick.on.net
Fri Oct 21 19:56:33 CEST 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 21 Oct 2011, at 01:33, Florian Haas wrote:

>>> Am I mad?  Should it work?
>> It does. We run DRBD + Pcmk + OCFS2 for testing. I would not use such a
>> setup in production though.
> Agree.

Thanks for your feedback.

FYI, I set it up to test it out, and it seemed to work.  The concerning part (aside from your advice to not use this architecture in production) was that during sync, which satisfyingly ran at a little over the 900,000,000 bps mark (according to tcpstat), the CPU utilisation of the associated kvm process would shoot up to 150-200% (4-CPU VM) and stay there for the duration of the synchronisation.  I suppose this is a QEMU/virtio/kvm IO mapping thing.  Perhaps SCSI passthrough would help here.

But based on your advice, I'll take another look at OCFS2, build a test environment inside the VMs, with the aim of installing it on the physical hosts for production. Will do everything possible to avoid split-brain.

Is there any easy and well defined way to set up a HA shared storage system with just two hosts, without using DRBD active/active?  NFS server+client on the same machine is problematic, but perhaps there's another method I haven't thought of.


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