TOPIC:

Hello,
I'm evaluating HA-Lizard and I was wondering why not directly use a Dual-Primary DRBD setup instead of an entire iSCSI stack (assuming a strict TWO servers cluster).

I maintain such a setup in some production installations and is working fine.
What I'm missing is the cluster automation (the reason why I'm evaluating HA-Lizard).

Even Linbit published a document for such a setup:
www.linbit.com/en/downloads/tech-guides

Am I missing anything ?? What is the reason requiring the iSCSI stack ??

Cheers,
Massimo

Hi Massimo,
Thank you for the question. Our goal with this project has always been centered on simplicity and resiliency. Although there are benefits to a dual primary setup, the downside can be a catastrophic loss of data if not implemented correctly. We also tried to introduce as few packages as possible into dom0.

In the end we felt that using the iSCSI support that is already part of XenServer would be the cleanest and least cluttered approach to expose the storage to the XenServer pool. This allowed us to achieve live migration without introducing a dual primary DRBD setup.

Thank you for your answer !
iSCSI approach is more resilient and less prone to disasters, for sure, anyway it hits I/O performance very hard.
A dual-primary approach requires roughly the same Dom0 packages and also allows live migration.

Maybe I'll start a new project to implement a dual-primary based HA-ISCSI replacement, only for the brave!

Thank you again.
Massimo

After 2 days of extensive testing the dual-primary approach is working really fine !
I'm using the drbd RPMs found in ISCSI-HA package.
The only tuning needed are some modification in drbd init script (force a "vgchange -an..." and a "drbdadm secondary..." before stopping).
So far so good!

Massimo

Hi Massimo,
Thanks for the update. Glad you got it working. Are you using dual-primary in conjunction with ha-lizard for HA? If you are interested in documenting and sharing your approach as part of our project, contact me offline at This email address is being protected from spambots. You need JavaScript enabled to view it.

Hello

We are also interested in a dual primary setup.
Are there any Documentation about this?

Do you already have any experience with it?
Which configuration files did you modified to run dual primary?